UI updated.

src/Squidex.Domain.Apps.Core.Model/Schemas/AssetsFieldProperties.cs

@@ -6,6 +6,7 @@
 //  All rights reserved.
 // ==========================================================================
 
+using System.Collections.Immutable;
 using Squidex.Infrastructure;
 
 namespace Squidex.Domain.Apps.Core.Schemas
@@ -13,8 +14,32 @@ namespace Squidex.Domain.Apps.Core.Schemas
     [TypeName(nameof(AssetsField))]
     public sealed class AssetsFieldProperties : FieldProperties
     {
+        private bool mustBeImage;
         private int? minItems;
         private int? maxItems;
+        private int? minWidth;
+        private int? maxWidth;
+        private int? minHeight;
+        private int? maxHeight;
+        private int? minSize;
+        private int? maxSize;
+        private int? aspectWidth;
+        private int? aspectHeight;
+        private ImmutableList<string> allowedExtensions;
+
+        public bool MustBeImage
+        {
+            get
+            {
+                return mustBeImage;
+            }
+            set
+            {
+                ThrowIfFrozen();
+
+                mustBeImage = value;
+            }
+        }
 
         public int? MinItems
         {
@@ -44,6 +69,132 @@ namespace Squidex.Domain.Apps.Core.Schemas
             }
         }
 
+        public int? MinWidth
+        {
+            get
+            {
+                return minWidth;
+            }
+            set
+            {
+                ThrowIfFrozen();
+
+                minWidth = value;
+            }
+        }
+
+        public int? MaxWidth
+        {
+            get
+            {
+                return maxWidth;
+            }
+            set
+            {
+                ThrowIfFrozen();
+
+                maxWidth = value;
+            }
+        }
+
+        public int? MinHeight
+        {
+            get
+            {
+                return minHeight;
+            }
+            set
+            {
+                ThrowIfFrozen();
+
+                minHeight = value;
+            }
+        }
+
+        public int? MaxHeight
+        {
+            get
+            {
+                return maxHeight;
+            }
+            set
+            {
+                ThrowIfFrozen();
+
+                maxHeight = value;
+            }
+        }
+
+        public int? MinSize
+        {
+            get
+            {
+                return minSize;
+            }
+            set
+            {
+                ThrowIfFrozen();
+
+                minSize = value;
+            }
+        }
+
+        public int? MaxSize
+        {
+            get
+            {
+                return maxSize;
+            }
+            set
+            {
+                ThrowIfFrozen();
+
+                maxSize = value;
+            }
+        }
+
+        public int? AspectWidth
+        {
+            get
+            {
+                return aspectWidth;
+            }
+            set
+            {
+                ThrowIfFrozen();
+
+                aspectWidth = value;
+            }
+        }
+
+        public int? AspectHeight
+        {
+            get
+            {
+                return aspectHeight;
+            }
+            set
+            {
+                ThrowIfFrozen();
+
+                aspectHeight = value;
+            }
+        }
+
+        public ImmutableList<string> AllowedExtensions
+        {
+            get
+            {
+                return allowedExtensions;
+            }
+            set
+            {
+                ThrowIfFrozen();
+
+                allowedExtensions = value;
+            }
+        }
+
         public override T Accept<T>(IFieldPropertiesVisitor<T> visitor)
         {
             return visitor.Visit(this);

src/Squidex.Domain.Apps.Core.Operations/ValidateContent/IAssetInfo.cs

@@ -0,0 +1,27 @@
+// ==========================================================================
+//  IAssetInfo.cs
+//  Squidex Headless CMS
+// ==========================================================================
+//  Copyright (c) Squidex Group
+//  All rights reserved.
+// ==========================================================================
+
+using System;
+
+namespace Squidex.Domain.Apps.Core.ValidateContent
+{
+    public interface IAssetInfo
+    {
+        Guid AssetId { get; }
+
+        long FileSize { get; }
+
+        bool IsImage { get; }
+
+        int? PixelWidth { get; }
+
+        int? PixelHeight { get; }
+
+        string FileName { get; }
+    }
+}

src/Squidex.Domain.Apps.Core.Operations/ValidateContent/ValidationContext.cs

@@ -16,20 +16,20 @@ namespace Squidex.Domain.Apps.Core.ValidateContent
     public sealed class ValidationContext
     {
         private readonly Func<IEnumerable<Guid>, Guid, Task<IReadOnlyList<Guid>>> checkContent;
-        private readonly Func<IEnumerable<Guid>, Task<IReadOnlyList<Guid>>> checkAsset;
+        private readonly Func<IEnumerable<Guid>, Task<IReadOnlyList<IAssetInfo>>> checkAsset;
 
         public bool IsOptional { get; }
 
         public ValidationContext(
             Func<IEnumerable<Guid>, Guid, Task<IReadOnlyList<Guid>>> checkContent,
-            Func<IEnumerable<Guid>, Task<IReadOnlyList<Guid>>> checkAsset)
+            Func<IEnumerable<Guid>, Task<IReadOnlyList<IAssetInfo>>> checkAsset)
             : this(checkContent, checkAsset, false)
         {
         }
 
         private ValidationContext(
             Func<IEnumerable<Guid>, Guid, Task<IReadOnlyList<Guid>>> checkContent,
-            Func<IEnumerable<Guid>, Task<IReadOnlyList<Guid>>> checkAsset,
+            Func<IEnumerable<Guid>, Task<IReadOnlyList<IAssetInfo>>> checkAsset,
             bool isOptional)
         {
             Guard.NotNull(checkAsset, nameof(checkAsset));
@@ -51,7 +51,7 @@ namespace Squidex.Domain.Apps.Core.ValidateContent
             return checkContent(contentIds, schemaId);
         }
 
-        public Task<IReadOnlyList<Guid>> GetInvalidAssetIdsAsync(IEnumerable<Guid> assetId)
+        public Task<IReadOnlyList<IAssetInfo>> GetAssetInfosAsync(IEnumerable<Guid> assetId)
         {
             return checkAsset(assetId);
         }

src/Squidex.Domain.Apps.Core.Operations/ValidateContent/Validators/AssetsValidator.cs

@@ -8,21 +8,111 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
+using Squidex.Domain.Apps.Core.Schemas;
+using Squidex.Infrastructure;
 
 namespace Squidex.Domain.Apps.Core.ValidateContent.Validators
 {
     public sealed class AssetsValidator : IValidator
     {
+        private readonly AssetsFieldProperties properties;
+
+        public AssetsValidator(AssetsFieldProperties properties)
+        {
+            this.properties = properties;
+        }
+
         public async Task ValidateAsync(object value, ValidationContext context, Action<string> addError)
         {
             if (value is ICollection<Guid> assetIds)
             {
-                var invalidIds = await context.GetInvalidAssetIdsAsync(assetIds);
+                var assets = await context.GetAssetInfosAsync(assetIds);
+                var i = 0;
 
-                foreach (var invalidId in invalidIds)
+                foreach (var assetId in assetIds)
                 {
-                    addError($"<FIELD> contains invalid asset '{invalidId}'.");
+                    i++;
+
+                    var asset = assets.FirstOrDefault(x => x.AssetId == assetId);
+
+                    void Error(string message)
+                    {
+                        addError($"<FIELD> has invalid asset #{i}: {message}");
+                    }
+
+                    if (asset == null)
+                    {
+                        Error($"Id '{assetId}' not found.");
+                        continue;
+                    }
+
+                    if (properties.MinSize.HasValue && asset.FileSize < properties.MinSize)
+                    {
+                        Error($"'{asset.FileSize.ToReadableSize()}' less than minimum of '{properties.MinSize.Value.ToReadableSize()}'.");
+                    }
+
+                    if (properties.MaxSize.HasValue && asset.FileSize > properties.MaxSize)
+                    {
+                        Error($"'{asset.FileSize.ToReadableSize()}' greater than maximum of '{properties.MaxSize.Value.ToReadableSize()}'.");
+                    }
+
+                    if (properties.AllowedExtensions != null &&
+                        properties.AllowedExtensions.Count > 0 &&
+                       !properties.AllowedExtensions.Any(x => asset.FileName.EndsWith("." + x, StringComparison.OrdinalIgnoreCase)))
+                    {
+                        Error("Invalid file extension.");
+                    }
+
+                    if (!asset.IsImage)
+                    {
+                        if (properties.MustBeImage)
+                        {
+                            Error("Not an image.");
+                        }
+
+                        continue;
+                    }
+
+                    if (asset.PixelWidth.HasValue &&
+                        asset.PixelHeight.HasValue)
+                    {
+                        var w = asset.PixelWidth.Value;
+                        var h = asset.PixelHeight.Value;
+
+                        var actualRatio = (double)w / h;
+
+                        if (properties.MinWidth.HasValue && w < properties.MinWidth)
+                        {
+                            Error($"Width '{w}px' less than minimum of '{properties.MinWidth}px'.");
+                        }
+
+                        if (properties.MaxWidth.HasValue && w > properties.MaxWidth)
+                        {
+                            Error($"Width '{w}px' greater than maximum of '{properties.MaxWidth}px'.");
+                        }
+
+                        if (properties.MinHeight.HasValue && h < properties.MinHeight)
+                        {
+                            Error($"Height '{h}px' less than minimum of '{properties.MinHeight}px'.");
+                        }
+
+                        if (properties.MaxHeight.HasValue && h > properties.MaxHeight)
+                        {
+                            Error($"Height '{h}px' greater than maximum of '{properties.MaxHeight}px'.");
+                        }
+
+                        if (properties.AspectHeight.HasValue && properties.AspectWidth.HasValue)
+                        {
+                            var expectedRatio = (double)properties.AspectWidth.Value / properties.AspectHeight.Value;
+
+                            if (Math.Abs(expectedRatio - actualRatio) > double.Epsilon)
+                            {
+                                Error($"Aspect ratio not '{properties.AspectWidth}:{properties.AspectHeight}'.");
+                            }
+                        }
+                    }
                 }
             }
         }

src/Squidex.Domain.Apps.Core.Operations/ValidateContent/ValidatorsFactory.cs

@@ -38,7 +38,7 @@ namespace Squidex.Domain.Apps.Core.ValidateContent
                 yield return new CollectionValidator<Guid>(properties.IsRequired, properties.MinItems, properties.MaxItems);
             }
 
-            yield return new AssetsValidator();
+            yield return new AssetsValidator(properties);
         }
 
         public IEnumerable<IValidator> Visit(BooleanFieldProperties properties)

src/Squidex.Domain.Apps.Read.MongoDb/Assets/MongoAssetEntity.cs

@@ -8,6 +8,7 @@
 
 using System;
 using MongoDB.Bson.Serialization.Attributes;
+using Squidex.Domain.Apps.Core.ValidateContent;
 using Squidex.Domain.Apps.Read.Assets;
 using Squidex.Infrastructure;
 using Squidex.Infrastructure.MongoDb;
@@ -65,5 +66,10 @@ namespace Squidex.Domain.Apps.Read.MongoDb.Assets
         [BsonRequired]
         [BsonElement]
         public RefToken LastModifiedBy { get; set; }
+
+        Guid IAssetInfo.AssetId
+        {
+            get { return Id; }
+        }
     }
 }

src/Squidex.Domain.Apps.Read.MongoDb/Assets/MongoAssetRepository.cs

@@ -39,15 +39,6 @@ namespace Squidex.Domain.Apps.Read.MongoDb.Assets
                     .Descending(x => x.LastModified));
         }
 
-        public async Task<IReadOnlyList<Guid>> QueryNotFoundAsync(Guid appId, IList<Guid> assetIds)
-        {
-            var assetEntities =
-                await Collection.Find(x => assetIds.Contains(x.Id) && x.AppId == appId).Project<BsonDocument>(Project.Include(x => x.Id))
-                    .ToListAsync();
-
-            return assetIds.Except(assetEntities.Select(x => Guid.Parse(x["_id"].AsString))).ToList();
-        }
-
         public async Task<IReadOnlyList<IAssetEntity>> QueryAsync(Guid appId, HashSet<string> mimeTypes = null, HashSet<Guid> ids = null, string query = null, int take = 10, int skip = 0)
         {
             var filter = CreateFilter(appId, mimeTypes, ids, query);

src/Squidex.Domain.Apps.Read.MongoDb/History/MongoHistoryEventEntity.cs

@@ -15,6 +15,7 @@ using Squidex.Infrastructure.MongoDb;
 namespace Squidex.Domain.Apps.Read.MongoDb.History
 {
     public sealed class MongoHistoryEventEntity : MongoEntity,
+        IEntity,
         IEntityWithAppRef,
         IUpdateableEntityWithVersion,
         IUpdateableEntityWithCreatedBy,

src/Squidex.Domain.Apps.Read/Assets/IAssetEntity.cs

@@ -6,22 +6,20 @@
 //  All rights reserved.
 // ==========================================================================
 
+using Squidex.Domain.Apps.Core.ValidateContent;
+
 namespace Squidex.Domain.Apps.Read.Assets
 {
-    public interface IAssetEntity : IEntityWithAppRef, IEntityWithCreatedBy, IEntityWithLastModifiedBy, IEntityWithVersion
+    public interface IAssetEntity :
+        IEntity,
+        IEntityWithAppRef,
+        IEntityWithCreatedBy,
+        IEntityWithLastModifiedBy,
+        IEntityWithVersion,
+        IAssetInfo
     {
         string MimeType { get; }
 
-        string FileName { get; }
-
-        long FileSize { get; }
-
         long FileVersion { get; }
-
-        bool IsImage { get; }
-
-        int? PixelWidth { get; }
-
-        int? PixelHeight { get; }
     }
 }

src/Squidex.Domain.Apps.Read/Assets/Repositories/IAssetRepository.cs

@@ -16,8 +16,6 @@ namespace Squidex.Domain.Apps.Read.Assets.Repositories
     {
         Task<IReadOnlyList<IAssetEntity>> QueryAsync(Guid appId, HashSet<string> mimeTypes = null, HashSet<Guid> ids = null, string query = null, int take = 10, int skip = 0);
 
-        Task<IReadOnlyList<Guid>> QueryNotFoundAsync(Guid appId, IList<Guid> assetIds);
-
         Task<IAssetEntity> FindAssetAsync(Guid id);
 
         Task<long> CountAsync(Guid appId, HashSet<string> mimeTypes = null, HashSet<Guid> ids = null, string query = null);

src/Squidex.Domain.Apps.Read/Contents/IContentEntity.cs

@@ -11,7 +11,12 @@ using Squidex.Domain.Apps.Core.Contents;
 
 namespace Squidex.Domain.Apps.Read.Contents
 {
-    public interface IContentEntity : IEntityWithAppRef, IEntityWithCreatedBy, IEntityWithLastModifiedBy, IEntityWithVersion
+    public interface IContentEntity :
+        IEntity,
+        IEntityWithAppRef,
+        IEntityWithCreatedBy,
+        IEntityWithLastModifiedBy,
+        IEntityWithVersion
     {
         Status Status { get; }
 

src/Squidex.Domain.Apps.Read/Contents/QueryContext.cs

@@ -53,7 +53,7 @@ namespace Squidex.Domain.Apps.Read.Contents
 
             if (asset == null)
             {
-                asset = await assetRepository.FindAssetAsync(id).ConfigureAwait(false);
+                asset = await assetRepository.FindAssetAsync(id);
 
                 if (asset != null)
                 {
@@ -70,7 +70,7 @@ namespace Squidex.Domain.Apps.Read.Contents
 
             if (content == null)
             {
-                content = (await contentQuery.FindContentAsync(app, schemaId.ToString(), user, id).ConfigureAwait(false)).Content;
+                content = (await contentQuery.FindContentAsync(app, schemaId.ToString(), user, id)).Content;
 
                 if (content != null)
                 {
@@ -95,14 +95,14 @@ namespace Squidex.Domain.Apps.Read.Contents
 
         public async Task<IReadOnlyList<IContentEntity>> QueryContentsAsync(string schemaIdOrName, string query)
         {
-            var contents = (await contentQuery.QueryWithCountAsync(app, schemaIdOrName, user, false, query).ConfigureAwait(false)).Items;
+            var contents = await contentQuery.QueryWithCountAsync(app, schemaIdOrName, user, false, query);
 
-            foreach (var content in contents)
+            foreach (var content in contents.Items)
             {
                 cachedContents[content.Id] = content;
             }
 
-            return contents;
+            return contents.Items;
         }
 
         public async Task<IReadOnlyList<IAssetEntity>> GetReferencedAssetsAsync(ICollection<Guid> ids)
@@ -113,7 +113,7 @@ namespace Squidex.Domain.Apps.Read.Contents
 
             if (notLoadedAssets.Count > 0)
             {
-                var assets = await assetRepository.QueryAsync(app.Id, null, notLoadedAssets, null, int.MaxValue).ConfigureAwait(false);
+                var assets = await assetRepository.QueryAsync(app.Id, null, notLoadedAssets, null, int.MaxValue);
 
                 foreach (var asset in assets)
                 {
@@ -132,9 +132,9 @@ namespace Squidex.Domain.Apps.Read.Contents
 
             if (notLoadedContents.Count > 0)
             {
-                var contents = (await contentQuery.QueryWithCountAsync(app, schemaId.ToString(), user, false, notLoadedContents).ConfigureAwait(false)).Items;
+                var contents = await contentQuery.QueryWithCountAsync(app, schemaId.ToString(), user, false, notLoadedContents);
 
-                foreach (var content in contents)
+                foreach (var content in contents.Items)
                 {
                     cachedContents[content.Id] = content;
                 }

src/Squidex.Domain.Apps.Read/History/IHistoryEventEntity.cs

@@ -15,10 +15,10 @@ namespace Squidex.Domain.Apps.Read.History
     {
         Guid EventId { get; }
 
+        RefToken Actor { get; }
+
         string Message { get; }
 
         long Version { get; }
-
-        RefToken Actor { get; }
     }
 }

src/Squidex.Domain.Apps.Read/IEntityWithAppRef.cs

@@ -10,7 +10,7 @@ using System;
 
 namespace Squidex.Domain.Apps.Read
 {
-    public interface IEntityWithAppRef : IEntity
+    public interface IEntityWithAppRef
     {
         Guid AppId { get; }
     }

src/Squidex.Domain.Apps.Read/Rules/IRuleEntity.cs

@@ -10,7 +10,12 @@ using Squidex.Domain.Apps.Core.Rules;
 
 namespace Squidex.Domain.Apps.Read.Rules
 {
-    public interface IRuleEntity : IEntityWithAppRef, IEntityWithCreatedBy, IEntityWithLastModifiedBy, IEntityWithVersion
+    public interface IRuleEntity :
+        IEntity,
+        IEntityWithAppRef,
+        IEntityWithCreatedBy,
+        IEntityWithLastModifiedBy,
+        IEntityWithVersion
     {
         Rule RuleDef { get; }
     }

src/Squidex.Domain.Apps.Read/Schemas/ISchemaEntity.cs

@@ -10,7 +10,12 @@ using Squidex.Domain.Apps.Core.Schemas;
 
 namespace Squidex.Domain.Apps.Read.Schemas
 {
-    public interface ISchemaEntity : IEntityWithAppRef, IEntityWithCreatedBy, IEntityWithLastModifiedBy, IEntityWithVersion
+    public interface ISchemaEntity :
+        IEntity,
+        IEntityWithAppRef,
+        IEntityWithCreatedBy,
+        IEntityWithLastModifiedBy,
+        IEntityWithVersion
     {
         string Name { get; }
 

src/Squidex.Domain.Apps.Write/Contents/ContentOperationContext.cs

@@ -84,11 +84,11 @@ namespace Squidex.Domain.Apps.Write.Contents
                     new ValidationContext(
                         (contentIds, schemaId) =>
                         {
-                            return contentRepository.QueryNotFoundAsync(appId, schemaId, contentIds.ToList());
+                            return QueryContentsAsync(appId, schemaId, contentIds);
                         },
                         assetIds =>
                         {
-                            return assetRepository.QueryNotFoundAsync(appId, assetIds.ToList());
+                            return QueryAssetsAsync(appId, assetIds);
                         });
 
                 if (partial)
@@ -107,6 +107,16 @@ namespace Squidex.Domain.Apps.Write.Contents
             }
         }
 
+        private async Task<IReadOnlyList<IAssetInfo>> QueryAssetsAsync(Guid appId, IEnumerable<Guid> assetIds)
+        {
+            return await assetRepository.QueryAsync(appId, null, new HashSet<Guid>(assetIds), null, int.MaxValue, 0);
+        }
+
+        private async Task<IReadOnlyList<Guid>> QueryContentsAsync(Guid appId, Guid schemaId, IEnumerable<Guid> contentIds)
+        {
+            return await contentRepository.QueryNotFoundAsync(appId, schemaId, contentIds.ToList());
+        }
+
         public Task ExecuteScriptAndTransformAsync(Func<ISchemaEntity, string> script, object operation)
         {
             if (command is ContentDataCommand dataCommand)

src/Squidex.Domain.Apps.Write/Schemas/Guards/FieldPropertiesValidator.cs

@@ -34,6 +34,34 @@ namespace Squidex.Domain.Apps.Write.Schemas.Guards
                     nameof(properties.MinItems),
                     nameof(properties.MaxItems));
             }
+
+            if (properties.MaxHeight.HasValue && properties.MinHeight.HasValue && properties.MinHeight.Value >= properties.MaxHeight.Value)
+            {
+                yield return new ValidationError("Max height must be greater than min height.",
+                    nameof(properties.MaxHeight),
+                    nameof(properties.MinHeight));
+            }
+
+            if (properties.MaxWidth.HasValue && properties.MinWidth.HasValue && properties.MinWidth.Value >= properties.MaxWidth.Value)
+            {
+                yield return new ValidationError("Max width must be greater than min width.",
+                    nameof(properties.MaxWidth),
+                    nameof(properties.MinWidth));
+            }
+
+            if (properties.MaxSize.HasValue && properties.MinSize.HasValue && properties.MinSize.Value >= properties.MaxSize.Value)
+            {
+                yield return new ValidationError("Max size must be greater than min size.",
+                    nameof(properties.MaxSize),
+                    nameof(properties.MinSize));
+            }
+
+            if (properties.AspectWidth.HasValue != properties.AspectHeight.HasValue)
+            {
+                yield return new ValidationError("Aspect width and height must be defined.",
+                    nameof(properties.AspectWidth),
+                    nameof(properties.AspectHeight));
+            }
         }
 
         public IEnumerable<ValidationError> Visit(BooleanFieldProperties properties)

src/Squidex.Infrastructure/FileExtensions.cs

@@ -36,6 +36,11 @@ namespace Squidex.Infrastructure
             }
         }
 
+        public static string ToReadableSize(this int value)
+        {
+            return ToReadableSize((long)value);
+        }
+
         public static string ToReadableSize(this long value)
         {
             if (value < 0)

src/Squidex.Infrastructure/States/StateFactory.cs

@@ -88,25 +88,25 @@ namespace Squidex.Infrastructure.States
 
             lock (lockObject)
             {
-                if (statesCache.TryGetValue<T>(key, out var state))
+                if (statesCache.TryGetValue<ObjectHolder<T, TState>>(key, out var stateObj))
                 {
-                    return Task.FromResult(state);
+                    return stateObj.ActivateAsync();
                 }
 
-                state = (T)services.GetService(typeof(T));
+                var state = (T)services.GetService(typeof(T));
 
                 var stateHolder = new StateHolder<TState>(key, () =>
                 {
                     pubSub.Publish(new InvalidateMessage { Key = key }, false);
                 }, store);
 
+                stateObj = new ObjectHolder<T, TState>(state, stateHolder);
+
                 statesCache.CreateEntry(key)
-                    .SetValue(state)
+                    .SetValue(stateObj)
                     .SetAbsoluteExpiration(CacheDuration)
                     .Dispose();
 
-                var stateObj = new ObjectHolder<T, TState>(state, stateHolder);
-
                 return stateObj.ActivateAsync();
             }
         }

src/Squidex/Areas/Api/Controllers/Schemas/Models/Converters/FieldPropertiesDtoFactory.cs

@@ -26,11 +26,6 @@ namespace Squidex.Areas.Api.Controllers.Schemas.Models.Converters
             return properties.Accept(Instance);
         }
 
-        public FieldPropertiesDto Visit(AssetsFieldProperties properties)
-        {
-            return SimpleMapper.Map(properties, new AssetsFieldPropertiesDto());
-        }
-
         public FieldPropertiesDto Visit(BooleanFieldProperties properties)
         {
             return SimpleMapper.Map(properties, new BooleanFieldPropertiesDto());
@@ -61,14 +56,20 @@ namespace Squidex.Areas.Api.Controllers.Schemas.Models.Converters
             return SimpleMapper.Map(properties, new TagsFieldPropertiesDto());
         }
 
+        public FieldPropertiesDto Visit(AssetsFieldProperties properties)
+        {
+            var result = SimpleMapper.Map(properties, new AssetsFieldPropertiesDto());
+
+            result.AllowedExtensions = properties.AllowedExtensions?.ToArray();
+
+            return result;
+        }
+
         public FieldPropertiesDto Visit(NumberFieldProperties properties)
         {
             var result = SimpleMapper.Map(properties, new NumberFieldPropertiesDto());
 
-            if (properties.AllowedValues != null)
-            {
-                result.AllowedValues = properties.AllowedValues.ToArray();
-            }
+            result.AllowedValues = properties.AllowedValues?.ToArray();
 
             return result;
         }
@@ -77,10 +78,7 @@ namespace Squidex.Areas.Api.Controllers.Schemas.Models.Converters
         {
             var result = SimpleMapper.Map(properties, new StringFieldPropertiesDto());
 
-            if (properties.AllowedValues != null)
-            {
-                result.AllowedValues = properties.AllowedValues.ToArray();
-            }
+            result.AllowedValues = properties.AllowedValues?.ToArray();
 
             return result;
         }

src/Squidex/Areas/Api/Controllers/Schemas/Models/Fields/AssetsFieldPropertiesDto.cs

@@ -6,6 +6,7 @@
 //  All rights reserved.
 // ==========================================================================
 
+using System.Collections.Immutable;
 using NJsonSchema.Annotations;
 using Squidex.Domain.Apps.Core.Schemas;
 using Squidex.Infrastructure.Reflection;
@@ -25,9 +26,66 @@ namespace Squidex.Areas.Api.Controllers.Schemas.Models.Fields
         /// </summary>
         public int? MaxItems { get; set; }
 
+        /// <summary>
+        /// The minimum file size in bytes.
+        /// </summary>
+        public int? MinSize { get; set; }
+
+        /// <summary>
+        /// The maximum file size in bytes.
+        /// </summary>
+        public int? MaxSize { get; set; }
+
+        /// <summary>
+        /// The minimum image width in pixels.
+        /// </summary>
+        public int? MinWidth { get; set; }
+
+        /// <summary>
+        /// The maximum image width in pixels.
+        /// </summary>
+        public int? MaxWidth { get; set; }
+
+        /// <summary>
+        /// The minimum image height in pixels.
+        /// </summary>
+        public int? MinHeight { get; set; }
+
+        /// <summary>
+        /// The maximum image height in pixels.
+        /// </summary>
+        public int? MaxHeight { get; set; }
+
+        /// <summary>
+        /// The image aspect width in pixels.
+        /// </summary>
+        public int? AspectWidth { get; set; }
+
+        /// <summary>
+        /// The image aspect height in pixels.
+        /// </summary>
+        public int? AspectHeight { get; set; }
+
+        /// <summary>
+        /// Defines if the asset must be an image.
+        /// </summary>
+        public bool MustBeImage { get; set; }
+
+        /// <summary>
+        /// The allowed file extensions.
+        /// </summary>
+        public string[] AllowedExtensions { get; set; }
+
         public override FieldProperties ToProperties()
         {
-            return SimpleMapper.Map(this, new AssetsFieldProperties());
+            var result = SimpleMapper.Map(this, new AssetsFieldProperties());
+
+            if (AllowedExtensions != null)
+            {
+                result.AllowedExtensions = ImmutableList.Create(AllowedExtensions);
+            }
+
+            return result;
         }
     }
 }

src/Squidex/app/features/administration/pages/users/user-page.component.html

@@ -32,9 +32,7 @@
         <div class="panel-main">
             <div class="panel-content panel-content-blank">
                 <div *ngIf="userFormError">
-                    <div class="form-alert form-alert-error">
-                        {{userFormError}}
-                    </div>
+                    <div class="form-alert form-alert-error" [innerHTML]="userFormError"></div>
                 </div>
 
                 <div class="form-group">

src/Squidex/app/features/schemas/pages/schema/field.component.html

@@ -74,8 +74,8 @@
                 </ul>
 
                 <div class="float-right">
-                    <button [disabled]="editFormSubmitted || field.isLocked" type="reset" class="btn btn-secondary" (click)="cancel()">Cancel</button>
-                    <button [disabled]="editFormSubmitted || field.isLocked" type="submit" class="btn btn-primary ml-1">Save</button>
+                    <button [disabled]="field.isLocked" type="reset" class="btn btn-secondary" (click)="cancel()">Cancel</button>
+                    <button [disabled]="field.isLocked" type="submit" class="btn btn-primary ml-1">Save</button>
                 </div>
             </div>
 

src/Squidex/app/features/schemas/pages/schema/types/assets-validation.component.html

@@ -10,13 +10,95 @@
     <div class="form-group row">
         <label class="col col-3 col-form-label">Items</label>
 
-        <div class="col col-3 minlength-col">
-            <input type="number" class="form-control" id="field-min-items" formControlName="minItems" placeholder="Min Items" />
+        <div class="col col-3 minmax-col">
+            <input type="number" class="form-control" id="field-min-items" formControlName="minItems" placeholder="Min Assets" />
             
-            <label class="col-form-label minitems-label">-</label>
+            <label class="col-form-label minmax-label">-</label>
         </div>
         <div class="col col-3">
-            <input type="number" class="form-control" id="field-max-items" formControlName="maxItems" placeholder="Max Items" />
+            <input type="number" class="form-control" id="field-max-items" formControlName="maxItems" placeholder="Max Assets" />
+        </div>
+    </div>
+    
+    <div class="form-group row">
+        <label class="col col-3 col-form-label">Size</label>
+
+        <div class="col col-3 minmax-col">
+            <input type="number" class="form-control" id="field-min-size" formControlName="minSize" placeholder="Min Size" />
+            
+            <label class="col-form-label minmax-label">-</label>
+        </div>
+        <div class="col col-3">
+            <input type="number" class="form-control" id="field-max-size" formControlName="maxSize" placeholder="Max Size" />
+        </div>
+        <div class="col col-3">            
+            <label class="col-form-label">bytes</label>
+        </div>
+    </div>
+    
+    <div class="form-group2 row">
+        <label class="col col-3 col-form-checkbox-label" for="field-must-be-image">Must be Image</label>
+
+        <div class="col col-6">
+            <input type="checkbox" class="form-check-input" id="field-must-be-image" formControlName="mustBeImage" />
+        </div>
+    </div>
+    
+    <div class="form-group row">
+        <label class="col col-3 col-form-label">Width</label>
+
+        <div class="col col-2 minmax-col">
+            <input type="number" class="form-control" id="field-min-width" formControlName="minWidth" />
+            
+            <label class="col-form-label minmax-label">-</label>
+        </div>
+        <div class="col col-2">
+            <input type="number" class="form-control" id="field-max-width" formControlName="maxWidth" />
+        </div>
+        <div class="col col-2">            
+            <label class="col-form-label">px</label>
+        </div>
+    </div>
+    
+    <div class="form-group row">
+        <label class="col col-3 col-form-label">Height</label>
+
+        <div class="col col-2 minmax-col">
+            <input type="number" class="form-control" id="field-min-height" formControlName="minHeight" />
+            
+            <label class="col-form-label minmax-label">-</label>
+        </div>
+        <div class="col col-2">
+            <input type="number" class="form-control" id="field-max-height" formControlName="maxHeight" />
+        </div>
+        <div class="col col-2">            
+            <label class="col-form-label">px</label>
+        </div>
+    </div>
+    
+    <div class="form-group row">
+        <label class="col col-3 col-form-label">AspectRatio</label>
+
+        <div class="col col-2 minmax-col">
+            <input type="number" class="form-control" id="field-aspect-height" formControlName="aspectWidth" placeholder="4" />
+            
+            <label class="col-form-label minmax-label">:</label>
+        </div>
+        <div class="col col-2">
+            <input type="number" class="form-control" id="field-aspect-height" formControlName="aspectHeight" placeholder="3" />
+        </div>
+        <div class="col col-2">            
+            <label class="col-form-label">px</label>
+        </div>
+    </div>
+    
+    <div class="form-group2 row">
+        <label for="field-allowed-values" class="col col-3 col-form-label">
+            Allowed Extensions
+        </label>
+
+        <div class="col col-6">
+            <sqx-tag-editor formControlName="allowedExtensions"></sqx-tag-editor>
         </div>
     </div>
 </div>

src/Squidex/app/features/schemas/pages/schema/types/assets-validation.component.scss

@@ -1,7 +1,7 @@
 @import '_vars';
 @import '_mixins';
 
-.minitems {
+.minmax {
     &-col {
         position: relative;
     }
@@ -17,4 +17,8 @@
 
 .form-group {
     margin-top: .5rem;
+}
+
+.form-group2 {
+    margin-top: 3rem;
 }

src/Squidex/app/features/schemas/pages/schema/types/assets-validation.component.ts

@@ -24,10 +24,40 @@ export class AssetsValidationComponent implements OnInit {
     public properties: AssetsFieldPropertiesDto;
 
     public ngOnInit() {
+        this.editForm.setControl('minItems',
+            new FormControl(this.properties.minItems));
+
         this.editForm.setControl('maxItems',
             new FormControl(this.properties.maxItems));
 
-        this.editForm.setControl('minItems',
-            new FormControl(this.properties.minItems));
+        this.editForm.setControl('minSize',
+            new FormControl(this.properties.minSize));
+
+        this.editForm.setControl('maxSize',
+            new FormControl(this.properties.maxSize));
+
+        this.editForm.setControl('allowedExtensions',
+            new FormControl(this.properties.allowedExtensions));
+
+        this.editForm.setControl('mustBeImage',
+            new FormControl(this.properties.mustBeImage));
+
+        this.editForm.setControl('minWidth',
+            new FormControl(this.properties.minWidth));
+
+        this.editForm.setControl('maxWidth',
+            new FormControl(this.properties.maxWidth));
+
+        this.editForm.setControl('minHeight',
+            new FormControl(this.properties.minHeight));
+
+        this.editForm.setControl('maxHeight',
+            new FormControl(this.properties.maxHeight));
+
+        this.editForm.setControl('aspectWidth',
+            new FormControl(this.properties.aspectWidth));
+
+        this.editForm.setControl('aspectHeight',
+            new FormControl(this.properties.aspectHeight));
     }
 }

src/Squidex/app/features/schemas/pages/schema/types/number-validation.component.html

@@ -10,10 +10,10 @@
     <div class="form-group row">
         <label class="col col-3 col-form-label">Range</label>
 
-        <div class="col col-3 minlength-col">
+        <div class="col col-3 minmax-col">
             <input type="number" class="form-control" id="field-min-value" formControlName="minValue" placeholder="Min Value" />
             
-            <label class="col-form-label minlength-label">-</label>
+            <label class="col-form-label minmax-label">-</label>
         </div>
         <div class="col col-3">
             <input type="number" class="form-control" id="field-max-value" formControlName="maxValue" placeholder="Max Value" />

src/Squidex/app/features/schemas/pages/schema/types/number-validation.component.scss

@@ -1,7 +1,7 @@
 @import '_vars';
 @import '_mixins';
 
-.minlength {
+.minmax {
     &-col {
         position: relative;
     }

src/Squidex/app/features/schemas/pages/schema/types/references-validation.component.html

@@ -20,10 +20,10 @@
     <div class="form-group row">
         <label class="col col-3 col-form-label">Items</label>
 
-        <div class="col col-3 minlength-col">
+        <div class="col col-3 minmax-col">
             <input type="number" class="form-control" id="field-min-items" formControlName="minItems" placeholder="Min Items" />
             
-            <label class="col-form-label minitems-label">-</label>
+            <label class="col-form-label minmax-label">-</label>
         </div>
         <div class="col col-3">
             <input type="number" class="form-control" id="field-max-items" formControlName="maxItems" placeholder="Max Items" />

src/Squidex/app/features/schemas/pages/schema/types/references-validation.component.scss

@@ -1,7 +1,7 @@
 @import '_vars';
 @import '_mixins';
 
-.minitems {
+.minmax {
     &-col {
         position: relative;
     }

src/Squidex/app/features/schemas/pages/schema/types/string-validation.component.html

@@ -10,10 +10,10 @@
     <div class="form-group row">
         <label class="col col-3 col-form-label">Length</label>
 
-        <div class="col col-3 minlength-col">
+        <div class="col col-3 minmax-col">
             <input type="number" class="form-control" id="field-min-length" formControlName="minLength" placeholder="Min Length" />
             
-            <label class="col-form-label minlength-label">-</label>
+            <label class="col-form-label minmax-label">-</label>
         </div>
         <div class="col col-3">
             <input type="number" class="form-control" id="field-max-length" formControlName="maxLength" placeholder="Max Length" />

src/Squidex/app/features/schemas/pages/schema/types/string-validation.component.scss

@@ -1,7 +1,7 @@
 @import '_vars';
 @import '_mixins';
 
-.minlength {
+.minmax {
     &-col {
         position: relative;
     }

src/Squidex/app/features/schemas/pages/schema/types/tags-validation.component.html

@@ -10,10 +10,10 @@
     <div class="form-group row">
         <label class="col col-3 col-form-label">Items</label>
 
-        <div class="col col-3 minlength-col">
+        <div class="col col-3 minmax-col">
             <input type="number" class="form-control" id="field-min-items" formControlName="minItems" placeholder="Min Items" />
             
-            <label class="col-form-label minitems-label">-</label>
+            <label class="col-form-label minmax-label">-</label>
         </div>
         <div class="col col-3">
             <input type="number" class="form-control" id="field-max-items" formControlName="maxItems" placeholder="Max Items" />

src/Squidex/app/features/schemas/pages/schema/types/tags-validation.component.scss

@@ -1,7 +1,7 @@
 @import '_vars';
 @import '_mixins';
 
-.minitems {
+.minmax {
     &-col {
         position: relative;
     }

src/Squidex/app/features/schemas/pages/schemas/schema-form.component.html

@@ -1,8 +1,6 @@
 <form [formGroup]="createForm" (ngSubmit)="createSchema()">
     <div *ngIf="createFormError">
-        <div class="form-alert form-alert-error">
-            {{createFormError}}
-        </div>
+        <div class="form-alert form-alert-error" [innerHTML]="createFormError"></div>
     </div>
 
 	<div class="form-group">

src/Squidex/app/framework/angular/control-errors.component.ts

@@ -16,7 +16,7 @@ const DEFAULT_ERRORS: { [key: string]: string } = {
     patternmessage: '{message}',
     minvalue: '{field} must be larger than {minValue}.',
     maxvalue: '{field} must be smaller than {maxValue}.',
-    minlength: '{field} must have a length of more than {requiredLength}.',
+    minmax: '{field} must have a length of more than {requiredLength}.',
     maxlength: '{field} must have a length of less than {requiredLength}.',
     match: '{message}',
     validdatetime: '{field} is not a valid date time',

src/Squidex/app/framework/angular/dialog-renderer.component.html

@@ -24,6 +24,6 @@
     <div class="alert alert-dismissible alert-{{notification.messageType}}" *ngFor="let notification of notifications" (click)="close(notification)" @fade>
         <button type="button" class="close" data-dismiss="alert" (close)="close(notification)">&times;</button>
 
-        {{notification.message}}
+        <span [innerHTML]="notification.message"></span>
     </div>
 </div>

src/Squidex/app/framework/angular/dialog-renderer.component.scss

@@ -4,12 +4,16 @@
 .notification-container {
     & {
         margin: .625rem;
-        max-width: 20rem;
-        min-width: 20rem;
+        max-width: 30rem;
+        min-width: 30rem;
         position: fixed;
         z-index: 100000;
     }
 
+    .alert {
+        max-height: 20rem;
+    }
+
     &-topright {
         @include fixed(0, 0, auto, auto);
     }

src/Squidex/app/framework/angular/http-extensions-impl.ts

@@ -19,29 +19,29 @@ export class Versioned<T> {
 }
 
 function formatMessage(message: string, details?: string[]) {
-    const parts: string[] = [];
+    const format = (row: string) => {
+        const last = row[row.length - 1];
 
-    const addPart = (p: string) => {
-        p = p.trim();
-
-        const c = p[p.length - 1];
-
-        if (c !== '.') {
-            p += '.';
+        if (last !== '.') {
+            return row + '.';
+        } else {
+            return row;
         }
-
-        parts.push(p);
     };
 
-    addPart(message);
+    let result = format(message);
 
     if (details) {
+        result = result + '<ul>';
+
         for (let d of details) {
-            addPart(d);
+            result += `<li>${format(d)}</li>`;
         }
+
+        result = result + '</ul>';
     }
 
-    return parts.join(' ');
+    return result;
 }
 
 export class ErrorDto {

src/Squidex/app/shared/services/schemas.service.ts

@@ -579,7 +579,17 @@ export class AssetsFieldPropertiesDto extends FieldPropertiesDto {
         isRequired: boolean,
         isListField: boolean,
         public readonly minItems?: number,
-        public readonly maxItems?: number
+        public readonly maxItems?: number,
+        public readonly minSize?: number,
+        public readonly maxSize?: number,
+        public readonly allowedExtensions?: string[],
+        public readonly mustBeImage?: boolean,
+        public readonly minWidth?: number,
+        public readonly maxWidth?: number,
+        public readonly minHeight?: number,
+        public readonly maxHeight?: number,
+        public readonly aspectWidth?: number,
+        public readonly aspectHeight?: number
     ) {
         super('Assets', label, hints, placeholder, isRequired, isListField);
     }

tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/AssetsFieldTests.cs

@@ -8,11 +8,13 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.Immutable;
 using System.Linq;
 using System.Threading.Tasks;
 using FluentAssertions;
 using Newtonsoft.Json.Linq;
 using Squidex.Domain.Apps.Core.Schemas;
+using Squidex.Domain.Apps.Core.ValidateContent;
 using Xunit;
 
 namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
@@ -21,22 +23,62 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
     {
         private readonly List<string> errors = new List<string>();
 
+        public sealed class AssetInfo : IAssetInfo
+        {
+            public Guid AssetId { get; set; }
+
+            public string FileName { get; set; }
+
+            public long FileSize { get; set; }
+
+            public bool IsImage { get; set; }
+
+            public int? PixelWidth { get; set; }
+
+            public int? PixelHeight { get; set; }
+        }
+
+        private readonly AssetInfo document = new AssetInfo
+        {
+            AssetId = Guid.NewGuid(),
+            FileName = "MyDocument.pdf",
+            FileSize = 1024 * 4,
+            IsImage = false,
+            PixelWidth = null,
+            PixelHeight = null
+        };
+
+        private readonly AssetInfo image = new AssetInfo
+        {
+            AssetId = Guid.NewGuid(),
+            FileName = "MyImage.png",
+            FileSize = 1024 * 8,
+            IsImage = true,
+            PixelWidth = 800,
+            PixelHeight = 600
+        };
+
+        private readonly ValidationContext ctx;
+
+        public AssetsFieldTests()
+        {
+            ctx = ValidationTestExtensions.Assets(image, document);
+        }
+
         [Fact]
         public void Should_instantiate_field()
         {
-            var sut = new AssetsField(1, "my-asset", Partitioning.Invariant);
+            var sut = Field(new AssetsFieldProperties());
 
-            Assert.Equal("my-asset", sut.Name);
+            Assert.Equal("my-assets", sut.Name);
         }
 
         [Fact]
         public async Task Should_not_add_error_if_assets_are_valid()
         {
-            var assetId = Guid.NewGuid();
-
-            var sut = new AssetsField(1, "my-asset", Partitioning.Invariant);
+            var sut = Field(new AssetsFieldProperties());
 
-            await sut.ValidateAsync(CreateValue(assetId), errors);
+            await sut.ValidateAsync(CreateValue(document.AssetId), errors, ctx);
 
             Assert.Empty(errors);
         }
@@ -44,9 +86,9 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_not_add_error_if_assets_are_null_and_valid()
         {
-            var sut = new AssetsField(1, "my-asset", Partitioning.Invariant);
+            var sut = Field(new AssetsFieldProperties());
 
-            await sut.ValidateAsync(CreateValue(null), errors);
+            await sut.ValidateAsync(CreateValue(null), errors, ctx);
 
             Assert.Empty(errors);
         }
@@ -54,9 +96,9 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_assets_are_required_and_null()
         {
-            var sut = new AssetsField(1, "my-asset", Partitioning.Invariant, new AssetsFieldProperties { IsRequired = true });
+            var sut = Field(new AssetsFieldProperties { IsRequired = true });
 
-            await sut.ValidateAsync(CreateValue(null), errors);
+            await sut.ValidateAsync(CreateValue(null), errors, ctx);
 
             errors.ShouldBeEquivalentTo(
                 new[] { "<FIELD> is required." });
@@ -65,9 +107,9 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_assets_are_required_and_empty()
         {
-            var sut = new AssetsField(1, "my-asset", Partitioning.Invariant, new AssetsFieldProperties { IsRequired = true });
+            var sut = Field(new AssetsFieldProperties { IsRequired = true });
 
-            await sut.ValidateAsync(CreateValue(), errors);
+            await sut.ValidateAsync(CreateValue(), errors, ctx);
 
             errors.ShouldBeEquivalentTo(
                 new[] { "<FIELD> is required." });
@@ -76,7 +118,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_is_not_valid()
         {
-            var sut = new AssetsField(1, "my-asset", Partitioning.Invariant);
+            var sut = Field(new AssetsFieldProperties());
 
             await sut.ValidateAsync("invalid", errors);
 
@@ -87,9 +129,9 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_has_not_enough_items()
         {
-            var sut = new AssetsField(1, "my-asset", Partitioning.Invariant, new AssetsFieldProperties { MinItems = 3 });
+            var sut = Field(new AssetsFieldProperties { MinItems = 3 });
 
-            await sut.ValidateAsync(CreateValue(Guid.NewGuid(), Guid.NewGuid()), errors);
+            await sut.ValidateAsync(CreateValue(document.AssetId, document.AssetId), errors, ctx);
 
             errors.ShouldBeEquivalentTo(
                 new[] { "<FIELD> must have at least 3 item(s)." });
@@ -98,9 +140,9 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_has_too_much_items()
         {
-            var sut = new AssetsField(1, "my-asset", Partitioning.Invariant, new AssetsFieldProperties { MaxItems = 1 });
+            var sut = Field(new AssetsFieldProperties { MaxItems = 1 });
 
-            await sut.ValidateAsync(CreateValue(Guid.NewGuid(), Guid.NewGuid()), errors);
+            await sut.ValidateAsync(CreateValue(document.AssetId, document.AssetId), errors, ctx);
 
             errors.ShouldBeEquivalentTo(
                 new[] { "<FIELD> must have not more than 1 item(s)." });
@@ -111,17 +153,125 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             var assetId = Guid.NewGuid();
 
-            var sut = new AssetsField(1, "my-asset", Partitioning.Invariant);
+            var sut = Field(new AssetsFieldProperties());
+
+            await sut.ValidateAsync(CreateValue(assetId), errors, ctx);
+
+            errors.ShouldBeEquivalentTo(
+                new[] { $"<FIELD> has invalid asset #1: Id '{assetId}' not found." });
+        }
+
+        [Fact]
+        public async Task Should_add_error_if_document_is_too_small()
+        {
+            var sut = Field(new AssetsFieldProperties { MinSize = 5 * 1024 });
+
+            await sut.ValidateAsync(CreateValue(document.AssetId, image.AssetId), errors, ctx);
+
+            errors.ShouldBeEquivalentTo(
+                new[] { $"<FIELD> has invalid asset #1: '4 kB' less than minimum of '5 kB'." });
+        }
+
+        [Fact]
+        public async Task Should_add_error_if_document_is_too_big()
+        {
+            var sut = Field(new AssetsFieldProperties { MaxSize = 5 * 1024 });
+
+            await sut.ValidateAsync(CreateValue(document.AssetId, image.AssetId), errors, ctx);
+
+            errors.ShouldBeEquivalentTo(
+                new[] { $"<FIELD> has invalid asset #2: '8 kB' greater than maximum of '5 kB'." });
+        }
+
+        [Fact]
+        public async Task Should_add_error_if_document_is_not_an_image()
+        {
+            var sut = Field(new AssetsFieldProperties { MustBeImage = true });
+
+            await sut.ValidateAsync(CreateValue(document.AssetId, image.AssetId), errors, ctx);
+
+            errors.ShouldBeEquivalentTo(
+                new[] { $"<FIELD> has invalid asset #1: Not an image." });
+        }
+
+        [Fact]
+        public async Task Should_add_error_if_image_width_is_too_small()
+        {
+            var sut = Field(new AssetsFieldProperties { MinWidth = 1000 });
+
+            await sut.ValidateAsync(CreateValue(document.AssetId, image.AssetId), errors, ctx);
+
+            errors.ShouldBeEquivalentTo(
+                new[] { $"<FIELD> has invalid asset #2: Width '800px' less than minimum of '1000px'." });
+        }
+
+        [Fact]
+        public async Task Should_add_error_if_image_width_is_too_big()
+        {
+            var sut = Field(new AssetsFieldProperties { MaxWidth = 700 });
+
+            await sut.ValidateAsync(CreateValue(document.AssetId, image.AssetId), errors, ctx);
+
+            errors.ShouldBeEquivalentTo(
+                new[] { $"<FIELD> has invalid asset #2: Width '800px' greater than maximum of '700px'." });
+        }
+
+        [Fact]
+        public async Task Should_add_error_if_image_height_is_too_small()
+        {
+            var sut = Field(new AssetsFieldProperties { MinHeight = 800 });
+
+            await sut.ValidateAsync(CreateValue(document.AssetId, image.AssetId), errors, ctx);
+
+            errors.ShouldBeEquivalentTo(
+                new[] { $"<FIELD> has invalid asset #2: Height '600px' less than minimum of '800px'." });
+        }
+
+        [Fact]
+        public async Task Should_add_error_if_image_height_is_too_big()
+        {
+            var sut = Field(new AssetsFieldProperties { MaxHeight = 500 });
+
+            await sut.ValidateAsync(CreateValue(document.AssetId, image.AssetId), errors, ctx);
+
+            errors.ShouldBeEquivalentTo(
+                new[] { $"<FIELD> has invalid asset #2: Height '600px' greater than maximum of '500px'." });
+        }
+
+        [Fact]
+        public async Task Should_add_error_if_image_has_invalid_aspect_ratio()
+        {
+            var sut = Field(new AssetsFieldProperties { AspectWidth = 1, AspectHeight = 1 });
 
-            await sut.ValidateAsync(CreateValue(assetId), errors, ValidationTestExtensions.InvalidContext(assetId));
+            await sut.ValidateAsync(CreateValue(document.AssetId, image.AssetId), errors, ctx);
 
             errors.ShouldBeEquivalentTo(
-                new[] { $"<FIELD> contains invalid asset '{assetId}'." });
+                new[] { "<FIELD> has invalid asset #2: Aspect ratio not '1:1'." });
+        }
+
+        [Fact]
+        public async Task Should_add_error_if_image_has_invalid_extension()
+        {
+            var sut = Field(new AssetsFieldProperties { AllowedExtensions = ImmutableList.Create("mp4") });
+
+            await sut.ValidateAsync(CreateValue(document.AssetId, image.AssetId), errors, ctx);
+
+            errors.ShouldBeEquivalentTo(
+                new[]
+                {
+                    $"<FIELD> has invalid asset #1: Invalid file extension.",
+                    $"<FIELD> has invalid asset #2: Invalid file extension."
+                });
         }
 
         private static JToken CreateValue(params Guid[] ids)
         {
             return ids == null ? JValue.CreateNull() : (JToken)new JArray(ids.OfType<object>().ToArray());
         }
+
+        private static AssetsField Field(AssetsFieldProperties properties)
+        {
+            return new AssetsField(1, "my-assets", Partitioning.Invariant, properties);
+        }
     }
 }

tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/BooleanFieldTests.cs

@@ -22,15 +22,15 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public void Should_instantiate_field()
         {
-            var sut = new BooleanField(1, "my-bolean", Partitioning.Invariant);
+            var sut = Field(new BooleanFieldProperties());
 
-            Assert.Equal("my-bolean", sut.Name);
+            Assert.Equal("my-boolean", sut.Name);
         }
 
         [Fact]
         public async Task Should_not_add_error_if_null_boolean_is_valid()
         {
-            var sut = new BooleanField(1, "my-bolean", Partitioning.Invariant);
+            var sut = Field(new BooleanFieldProperties());
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -40,7 +40,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_not_add_error_if_boolean_is_valid()
         {
-            var sut = new BooleanField(1, "my-bolean", Partitioning.Invariant);
+            var sut = Field(new BooleanFieldProperties());
 
             await sut.ValidateAsync(CreateValue(true), errors);
 
@@ -50,7 +50,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_boolean_is_required()
         {
-            var sut = new BooleanField(1, "my-bolean", Partitioning.Invariant, new BooleanFieldProperties { IsRequired = true });
+            var sut = Field(new BooleanFieldProperties { IsRequired = true });
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -61,7 +61,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_is_not_valid()
         {
-            var sut = new BooleanField(1, "my-bolean", Partitioning.Invariant);
+            var sut = Field(new BooleanFieldProperties());
 
             await sut.ValidateAsync(CreateValue("Invalid"), errors);
 
@@ -73,5 +73,10 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             return new JValue(v);
         }
+
+        private static BooleanField Field(BooleanFieldProperties properties)
+        {
+            return new BooleanField(1, "my-boolean", Partitioning.Invariant, properties);
+        }
     }
 }

tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/DateTimeFieldTests.cs

@@ -24,7 +24,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public void Should_instantiate_field()
         {
-            var sut = new DateTimeField(1, "my-datetime", Partitioning.Invariant);
+            var sut = Field(new DateTimeFieldProperties());
 
             Assert.Equal("my-datetime", sut.Name);
         }
@@ -32,7 +32,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_not_add_error_if_datetime_is_valid()
         {
-            var sut = new DateTimeField(1, "my-datetime", Partitioning.Invariant);
+            var sut = Field(new DateTimeFieldProperties());
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -42,7 +42,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_datetime_is_required()
         {
-            var sut = new DateTimeField(1, "my-datetime", Partitioning.Invariant, new DateTimeFieldProperties { IsRequired = true });
+            var sut = Field(new DateTimeFieldProperties { IsRequired = true });
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -53,7 +53,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_datetime_is_less_than_min()
         {
-            var sut = new DateTimeField(1, "my-datetime", Partitioning.Invariant, new DateTimeFieldProperties { MinValue = FutureDays(10) });
+            var sut = Field(new DateTimeFieldProperties { MinValue = FutureDays(10) });
 
             await sut.ValidateAsync(CreateValue(FutureDays(0)), errors);
 
@@ -64,7 +64,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_datetime_is_greater_than_max()
         {
-            var sut = new DateTimeField(1, "my-datetime", Partitioning.Invariant, new DateTimeFieldProperties { MaxValue = FutureDays(10) });
+            var sut = Field(new DateTimeFieldProperties { MaxValue = FutureDays(10) });
 
             await sut.ValidateAsync(CreateValue(FutureDays(20)), errors);
 
@@ -75,7 +75,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_is_not_valid()
         {
-            var sut = new DateTimeField(1, "my-datetime", Partitioning.Invariant);
+            var sut = Field(new DateTimeFieldProperties());
 
             await sut.ValidateAsync(CreateValue("Invalid"), errors);
 
@@ -86,7 +86,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_is_another_type()
         {
-            var sut = new DateTimeField(1, "my-datetime", Partitioning.Invariant);
+            var sut = Field(new DateTimeFieldProperties());
 
             await sut.ValidateAsync(CreateValue(123), errors);
 
@@ -103,5 +103,10 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             return v is Instant ? new JValue(v.ToString()) : new JValue(v);
         }
+
+        private static DateTimeField Field(DateTimeFieldProperties properties)
+        {
+            return new DateTimeField(1, "my-datetime", Partitioning.Invariant, properties);
+        }
     }
 }

tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/GeolocationFieldTests.cs

@@ -22,7 +22,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public void Should_instantiate_field()
         {
-            var sut = new GeolocationField(1, "my-geolocation", Partitioning.Invariant);
+            var sut = Field(new GeolocationFieldProperties());
 
             Assert.Equal("my-geolocation", sut.Name);
         }
@@ -30,7 +30,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_not_add_error_if_geolocation_is_valid_null()
         {
-            var sut = new GeolocationField(1, "my-geolocation", Partitioning.Invariant);
+            var sut = Field(new GeolocationFieldProperties());
 
             await sut.ValidateAsync(CreateValue(JValue.CreateNull()), errors);
 
@@ -40,7 +40,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_not_add_error_if_geolocation_is_valid()
         {
-            var sut = new GeolocationField(1, "my-geolocation", Partitioning.Invariant);
+            var sut = Field(new GeolocationFieldProperties());
 
             var geolocation = new JObject(
                 new JProperty("latitude", 0),
@@ -54,7 +54,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_geolocation_has_invalid_latitude()
         {
-            var sut = new GeolocationField(1, "my-geolocation", Partitioning.Invariant, new GeolocationFieldProperties { IsRequired = true });
+            var sut = Field(new GeolocationFieldProperties { IsRequired = true });
 
             var geolocation = new JObject(
                 new JProperty("latitude", 200),
@@ -69,7 +69,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_geolocation_has_invalid_longitude()
         {
-            var sut = new GeolocationField(1, "my-geolocation", Partitioning.Invariant, new GeolocationFieldProperties { IsRequired = true });
+            var sut = Field(new GeolocationFieldProperties { IsRequired = true });
 
             var geolocation = new JObject(
                 new JProperty("latitude", 0),
@@ -84,7 +84,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_geolocation_has_too_many_properties()
         {
-            var sut = new GeolocationField(1, "my-geolocation", Partitioning.Invariant, new GeolocationFieldProperties { IsRequired = true });
+            var sut = Field(new GeolocationFieldProperties { IsRequired = true });
 
             var geolocation = new JObject(
                 new JProperty("invalid", 0),
@@ -100,7 +100,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_geolocation_is_required()
         {
-            var sut = new GeolocationField(1, "my-geolocation", Partitioning.Invariant, new GeolocationFieldProperties { IsRequired = true });
+            var sut = Field(new GeolocationFieldProperties { IsRequired = true });
 
             await sut.ValidateAsync(CreateValue(JValue.CreateNull()), errors);
 
@@ -112,5 +112,10 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             return v;
         }
+
+        private static GeolocationField Field(GeolocationFieldProperties properties)
+        {
+            return new GeolocationField(1, "my-geolocation", Partitioning.Invariant, properties);
+        }
     }
 }

tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/JsonFieldTests.cs

@@ -22,7 +22,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public void Should_instantiate_field()
         {
-            var sut = new JsonField(1, "my-json", Partitioning.Invariant);
+            var sut = Field(new JsonFieldProperties());
 
             Assert.Equal("my-json", sut.Name);
         }
@@ -30,7 +30,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_not_add_error_if_json_is_valid()
         {
-            var sut = new JsonField(1, "my-json", Partitioning.Invariant);
+            var sut = Field(new JsonFieldProperties());
 
             await sut.ValidateAsync(CreateValue(new JValue(1)), errors);
 
@@ -40,7 +40,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_json_is_required()
         {
-            var sut = new JsonField(1, "my-json", Partitioning.Invariant, new JsonFieldProperties { IsRequired = true });
+            var sut = Field(new JsonFieldProperties { IsRequired = true });
 
             await sut.ValidateAsync(CreateValue(JValue.CreateNull()), errors);
 
@@ -52,5 +52,10 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             return v;
         }
+
+        private static JsonField Field(JsonFieldProperties properties)
+        {
+            return new JsonField(1, "my-json", Partitioning.Invariant, properties);
+        }
     }
 }

tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/NumberFieldTests.cs

@@ -23,7 +23,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public void Should_instantiate_field()
         {
-            var sut = new NumberField(1, "my-number", Partitioning.Invariant);
+            var sut = Field(new NumberFieldProperties());
 
             Assert.Equal("my-number", sut.Name);
         }
@@ -31,7 +31,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_not_add_error_if_number_is_valid()
         {
-            var sut = new NumberField(1, "my-number", Partitioning.Invariant);
+            var sut = Field(new NumberFieldProperties());
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -41,7 +41,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_number_is_required()
         {
-            var sut = new NumberField(1, "my-number", Partitioning.Invariant, new NumberFieldProperties { IsRequired = true });
+            var sut = Field(new NumberFieldProperties { IsRequired = true });
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -52,7 +52,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_number_is_less_than_min()
         {
-            var sut = new NumberField(1, "my-number", Partitioning.Invariant, new NumberFieldProperties { MinValue = 10 });
+            var sut = Field(new NumberFieldProperties { MinValue = 10 });
 
             await sut.ValidateAsync(CreateValue(5), errors);
 
@@ -63,7 +63,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_number_is_greater_than_max()
         {
-            var sut = new NumberField(1, "my-number", Partitioning.Invariant, new NumberFieldProperties { MaxValue = 10 });
+            var sut = Field(new NumberFieldProperties { MaxValue = 10 });
 
             await sut.ValidateAsync(CreateValue(20), errors);
 
@@ -74,7 +74,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_number_is_not_allowed()
         {
-            var sut = new NumberField(1, "my-number", Partitioning.Invariant, new NumberFieldProperties { AllowedValues = ImmutableList.Create(10d) });
+            var sut = Field(new NumberFieldProperties { AllowedValues = ImmutableList.Create(10d) });
 
             await sut.ValidateAsync(CreateValue(20), errors);
 
@@ -85,7 +85,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_is_not_valid()
         {
-            var sut = new NumberField(1, "my-number", Partitioning.Invariant);
+            var sut = Field(new NumberFieldProperties());
 
             await sut.ValidateAsync(CreateValue("Invalid"), errors);
 
@@ -97,5 +97,10 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             return new JValue(v);
         }
+
+        private static NumberField Field(NumberFieldProperties properties)
+        {
+            return new NumberField(1, "my-number", Partitioning.Invariant, properties);
+        }
     }
 }

tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/ReferencesFieldTests.cs

@@ -25,7 +25,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public void Should_instantiate_field()
         {
-            var sut = new ReferencesField(1, "my-refs", Partitioning.Invariant);
+            var sut = Field(new ReferencesFieldProperties());
 
             Assert.Equal("my-refs", sut.Name);
         }
@@ -35,7 +35,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             var referenceId = Guid.NewGuid();
 
-            var sut = new ReferencesField(1, "my-refs", Partitioning.Invariant);
+            var sut = Field(new ReferencesFieldProperties());
 
             await sut.ValidateAsync(CreateValue(referenceId), errors, ValidationTestExtensions.ValidContext);
 
@@ -45,7 +45,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_not_add_error_if_references_are_null_and_valid()
         {
-            var sut = new ReferencesField(1, "my-refs", Partitioning.Invariant);
+            var sut = Field(new ReferencesFieldProperties());
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -55,7 +55,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_references_are_required_and_null()
         {
-            var sut = new ReferencesField(1, "my-refs", Partitioning.Invariant, new ReferencesFieldProperties { SchemaId = schemaId, IsRequired = true });
+            var sut = Field(new ReferencesFieldProperties { SchemaId = schemaId, IsRequired = true });
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -66,7 +66,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_references_are_required_and_empty()
         {
-            var sut = new ReferencesField(1, "my-refs", Partitioning.Invariant, new ReferencesFieldProperties { SchemaId = schemaId, IsRequired = true });
+            var sut = Field(new ReferencesFieldProperties { SchemaId = schemaId, IsRequired = true });
 
             await sut.ValidateAsync(CreateValue(), errors);
 
@@ -77,7 +77,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_is_not_valid()
         {
-            var sut = new ReferencesField(1, "my-refs", Partitioning.Invariant);
+            var sut = Field(new ReferencesFieldProperties());
 
             await sut.ValidateAsync("invalid", errors);
 
@@ -88,7 +88,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_has_not_enough_items()
         {
-            var sut = new ReferencesField(1, "my-refs", Partitioning.Invariant, new ReferencesFieldProperties { SchemaId = schemaId, MinItems = 3 });
+            var sut = Field(new ReferencesFieldProperties { SchemaId = schemaId, MinItems = 3 });
 
             await sut.ValidateAsync(CreateValue(Guid.NewGuid(), Guid.NewGuid()), errors);
 
@@ -99,7 +99,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_has_too_much_items()
         {
-            var sut = new ReferencesField(1, "my-refs", Partitioning.Invariant, new ReferencesFieldProperties { SchemaId = schemaId, MaxItems = 1 });
+            var sut = Field(new ReferencesFieldProperties { SchemaId = schemaId, MaxItems = 1 });
 
             await sut.ValidateAsync(CreateValue(Guid.NewGuid(), Guid.NewGuid()), errors);
 
@@ -112,9 +112,9 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             var referenceId = Guid.NewGuid();
 
-            var sut = new ReferencesField(1, "my-refs", Partitioning.Invariant, new ReferencesFieldProperties { SchemaId = schemaId });
+            var sut = Field(new ReferencesFieldProperties { SchemaId = schemaId });
 
-            await sut.ValidateAsync(CreateValue(referenceId), errors, ValidationTestExtensions.InvalidContext(referenceId));
+            await sut.ValidateAsync(CreateValue(referenceId), errors, ValidationTestExtensions.InvalidReferences(referenceId));
 
             errors.ShouldBeEquivalentTo(
                 new[] { $"<FIELD> contains invalid reference '{referenceId}'." });
@@ -124,5 +124,10 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             return ids == null ? JValue.CreateNull() : (JToken)new JArray(ids.OfType<object>().ToArray());
         }
+
+        private static ReferencesField Field(ReferencesFieldProperties properties)
+        {
+            return new ReferencesField(1, "my-refs", Partitioning.Invariant, properties);
+        }
     }
 }

tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/StringFieldTests.cs

@@ -23,7 +23,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public void Should_instantiate_field()
         {
-            var sut = new StringField(1, "my-string", Partitioning.Invariant);
+            var sut = Field(new StringFieldProperties());
 
             Assert.Equal("my-string", sut.Name);
         }
@@ -31,7 +31,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_not_add_error_if_string_is_valid()
         {
-            var sut = new StringField(1, "my-string", Partitioning.Invariant, new StringFieldProperties { Label = "<FIELD>" });
+            var sut = Field(new StringFieldProperties { Label = "<FIELD>" });
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -41,7 +41,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_string_is_required()
         {
-            var sut = new StringField(1, "my-string", Partitioning.Invariant, new StringFieldProperties { IsRequired = true });
+            var sut = Field(new StringFieldProperties { IsRequired = true });
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -52,7 +52,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_string_is_shorter_than_min_length()
         {
-            var sut = new StringField(1, "my-string", Partitioning.Invariant, new StringFieldProperties { MinLength = 10 });
+            var sut = Field(new StringFieldProperties { MinLength = 10 });
 
             await sut.ValidateAsync(CreateValue("123"), errors);
 
@@ -63,7 +63,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_string_is_longer_than_max_length()
         {
-            var sut = new StringField(1, "my-string", Partitioning.Invariant, new StringFieldProperties { MaxLength = 5 });
+            var sut = Field(new StringFieldProperties { MaxLength = 5 });
 
             await sut.ValidateAsync(CreateValue("12345678"), errors);
 
@@ -74,7 +74,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_string_not_allowed()
         {
-            var sut = new StringField(1, "my-string", Partitioning.Invariant, new StringFieldProperties { AllowedValues = ImmutableList.Create("Foo") });
+            var sut = Field(new StringFieldProperties { AllowedValues = ImmutableList.Create("Foo") });
 
             await sut.ValidateAsync(CreateValue("Bar"), errors);
 
@@ -85,7 +85,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_number_is_not_valid_pattern()
         {
-            var sut = new StringField(1, "my-string", Partitioning.Invariant, new StringFieldProperties { Pattern = "[0-9]{3}" });
+            var sut = Field(new StringFieldProperties { Pattern = "[0-9]{3}" });
 
             await sut.ValidateAsync(CreateValue("abc"), errors);
 
@@ -96,7 +96,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_number_is_not_valid_pattern_with_message()
         {
-            var sut = new StringField(1, "my-string", Partitioning.Invariant, new StringFieldProperties { Pattern = "[0-9]{3}", PatternMessage = "Custom Error Message." });
+            var sut = Field(new StringFieldProperties { Pattern = "[0-9]{3}", PatternMessage = "Custom Error Message." });
 
             await sut.ValidateAsync(CreateValue("abc"), errors);
 
@@ -108,5 +108,10 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             return new JValue(v);
         }
+
+        private static StringField Field(StringFieldProperties properties)
+        {
+            return new StringField(1, "my-string", Partitioning.Invariant, properties);
+        }
     }
 }

tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/TagsFieldTests.cs

@@ -24,7 +24,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public void Should_instantiate_field()
         {
-            var sut = new TagsField(1, "my-tags", Partitioning.Invariant);
+            var sut = Field(new TagsFieldProperties());
 
             Assert.Equal("my-tags", sut.Name);
         }
@@ -34,7 +34,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             var referenceId = Guid.NewGuid();
 
-            var sut = new TagsField(1, "my-tags", Partitioning.Invariant);
+            var sut = Field(new TagsFieldProperties());
 
             await sut.ValidateAsync(CreateValue(referenceId), errors, ValidationTestExtensions.ValidContext);
 
@@ -44,7 +44,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_not_add_error_if_tags_are_null_and_valid()
         {
-            var sut = new TagsField(1, "my-tags", Partitioning.Invariant);
+            var sut = Field(new TagsFieldProperties());
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -54,7 +54,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_tags_are_required_and_null()
         {
-            var sut = new TagsField(1, "my-tags", Partitioning.Invariant, new TagsFieldProperties { IsRequired = true });
+            var sut = Field(new TagsFieldProperties { IsRequired = true });
 
             await sut.ValidateAsync(CreateValue(null), errors);
 
@@ -65,7 +65,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_tags_are_required_and_empty()
         {
-            var sut = new TagsField(1, "my-tags", Partitioning.Invariant, new TagsFieldProperties { IsRequired = true });
+            var sut = Field(new TagsFieldProperties { IsRequired = true });
 
             await sut.ValidateAsync(CreateValue(), errors);
 
@@ -76,7 +76,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_is_not_valid()
         {
-            var sut = new TagsField(1, "my-tags", Partitioning.Invariant);
+            var sut = Field(new TagsFieldProperties());
 
             await sut.ValidateAsync("invalid", errors);
 
@@ -87,7 +87,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_has_not_enough_items()
         {
-            var sut = new TagsField(1, "my-tags", Partitioning.Invariant, new TagsFieldProperties { MinItems = 3 });
+            var sut = Field(new TagsFieldProperties { MinItems = 3 });
 
             await sut.ValidateAsync(CreateValue(Guid.NewGuid(), Guid.NewGuid()), errors);
 
@@ -98,7 +98,7 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         [Fact]
         public async Task Should_add_errors_if_value_has_too_much_items()
         {
-            var sut = new TagsField(1, "my-tags", Partitioning.Invariant, new TagsFieldProperties { MaxItems = 1 });
+            var sut = Field(new TagsFieldProperties { MaxItems = 1 });
 
             await sut.ValidateAsync(CreateValue(Guid.NewGuid(), Guid.NewGuid()), errors);
 
@@ -110,5 +110,10 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
         {
             return ids == null ? JValue.CreateNull() : (JToken)new JArray(ids.OfType<object>().ToArray());
         }
+
+        private static TagsField Field(TagsFieldProperties properties)
+        {
+            return new TagsField(1, "my-tags", Partitioning.Invariant, properties);
+        }
     }
 }

tests/Squidex.Domain.Apps.Core.Tests/Operations/ValidateContent/ValidationTestExtensions.cs

@@ -8,6 +8,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
 using Newtonsoft.Json.Linq;
 using Squidex.Domain.Apps.Core.Schemas;
@@ -18,9 +19,10 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
 {
     public static class ValidationTestExtensions
     {
-        private static readonly Task<IReadOnlyList<Guid>> ValidIds = Task.FromResult<IReadOnlyList<Guid>>(new List<Guid>());
+        private static readonly Task<IReadOnlyList<Guid>> ValidReferences = Task.FromResult<IReadOnlyList<Guid>>(new List<Guid>());
+        private static readonly Task<IReadOnlyList<IAssetInfo>> ValidAssets = Task.FromResult<IReadOnlyList<IAssetInfo>>(new List<IAssetInfo>());
 
-        public static readonly ValidationContext ValidContext = new ValidationContext((x, y) => ValidIds, x => ValidIds);
+        public static readonly ValidationContext ValidContext = new ValidationContext((x, y) => ValidReferences, x => ValidAssets);
 
         public static Task ValidateAsync(this IValidator validator, object value, IList<string> errors, ValidationContext context = null)
         {
@@ -42,11 +44,18 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
             return field.ValidateAsync(value, (context ?? ValidContext).Optional(true), errors.Add);
         }
 
-        public static ValidationContext InvalidContext(Guid assetId)
+        public static ValidationContext Assets(params IAssetInfo[] assets)
         {
-            var invalidIds = Task.FromResult<IReadOnlyList<Guid>>(new List<Guid> { assetId });
+            var actual = Task.FromResult<IReadOnlyList<IAssetInfo>>(assets.ToList());
 
-            return new ValidationContext((x, y) => invalidIds, x => invalidIds);
+            return new ValidationContext((x, y) => ValidReferences, x => actual);
+        }
+
+        public static ValidationContext InvalidReferences(Guid referencesIds)
+        {
+            var actual = Task.FromResult<IReadOnlyList<Guid>>(new List<Guid> { referencesIds });
+
+            return new ValidationContext((x, y) => actual, x => ValidAssets);
         }
     }
 }

tests/Squidex.Domain.Apps.Read.Tests/Contents/TestData/FakeAssetEntity.cs

@@ -19,6 +19,8 @@ namespace Squidex.Domain.Apps.Read.Contents.TestData
 
         public Guid AppId { get; set; }
 
+        public Guid AssetId { get; set; }
+
         public Instant Created { get; set; }
 
         public Instant LastModified { get; set; }

tests/Squidex.Domain.Apps.Write.Tests/Schemas/Guards/FieldProperties/AssetsFieldPropertiesTests.cs

@@ -18,7 +18,7 @@ namespace Squidex.Domain.Apps.Write.Schemas.Guards.FieldProperties
     public class AssetsFieldPropertiesTests
     {
         [Fact]
-        public void Should_add_error_if_min_greater_than_max()
+        public void Should_add_error_if_min_items_greater_than_max_items()
         {
             var sut = new AssetsFieldProperties { MinItems = 10, MaxItems = 5 };
 
@@ -30,5 +30,75 @@ namespace Squidex.Domain.Apps.Write.Schemas.Guards.FieldProperties
                     new ValidationError("Max items must be greater than min items.", "MinItems", "MaxItems")
                 });
         }
+
+        [Fact]
+        public void Should_add_error_if_min_width_greater_than_max_width()
+        {
+            var sut = new AssetsFieldProperties { MinWidth = 10, MaxWidth = 5 };
+
+            var errors = FieldPropertiesValidator.Validate(sut).ToList();
+
+            errors.ShouldBeEquivalentTo(
+                new List<ValidationError>
+                {
+                    new ValidationError("Max width must be greater than min width.", "MinWidth", "MaxWidth")
+                });
+        }
+
+        [Fact]
+        public void Should_add_error_if_min_height_greater_than_max_height()
+        {
+            var sut = new AssetsFieldProperties { MinHeight = 10, MaxHeight = 5 };
+
+            var errors = FieldPropertiesValidator.Validate(sut).ToList();
+
+            errors.ShouldBeEquivalentTo(
+                new List<ValidationError>
+                {
+                    new ValidationError("Max height must be greater than min height.", "MinHeight", "MaxHeight")
+                });
+        }
+
+        [Fact]
+        public void Should_add_error_if_min_size_greater_than_max_size()
+        {
+            var sut = new AssetsFieldProperties { MinSize = 10, MaxSize = 5 };
+
+            var errors = FieldPropertiesValidator.Validate(sut).ToList();
+
+            errors.ShouldBeEquivalentTo(
+                new List<ValidationError>
+                {
+                    new ValidationError("Max size must be greater than min size.", "MinSize", "MaxSize")
+                });
+        }
+
+        [Fact]
+        public void Should_add_error_if_only_aspect_width_is_defined()
+        {
+            var sut = new AssetsFieldProperties { AspectWidth = 10 };
+
+            var errors = FieldPropertiesValidator.Validate(sut).ToList();
+
+            errors.ShouldBeEquivalentTo(
+                new List<ValidationError>
+                {
+                    new ValidationError("Aspect width and height must be defined.", "AspectWidth", "AspectHeight")
+                });
+        }
+
+        [Fact]
+        public void Should_add_error_if_only_aspect_height_is_defined()
+        {
+            var sut = new AssetsFieldProperties { AspectHeight = 10 };
+
+            var errors = FieldPropertiesValidator.Validate(sut).ToList();
+
+            errors.ShouldBeEquivalentTo(
+                new List<ValidationError>
+                {
+                    new ValidationError("Aspect width and height must be defined.", "AspectWidth", "AspectHeight")
+                });
+        }
     }
 }