Use interface when possible.

src/Squidex.Domain.Apps.Core.Operations/EnrichContent/ContentEnricher.cs

@@ -50,7 +50,7 @@ namespace Squidex.Domain.Apps.Core.EnrichContent
             }
         }
 
-        private static void Enrich(Field field, ContentFieldData fieldData, IFieldPartitionItem partitionItem)
+        private static void Enrich(IField field, ContentFieldData fieldData, IFieldPartitionItem partitionItem)
         {
             Guard.NotNull(fieldData, nameof(fieldData));
 

src/Squidex.Domain.Apps.Core.Operations/EnrichContent/DefaultValueFactory.cs

@@ -22,7 +22,7 @@ namespace Squidex.Domain.Apps.Core.EnrichContent
             this.now = now;
         }
 
-        public static JToken CreateDefaultValue(Field field, Instant now)
+        public static JToken CreateDefaultValue(IField field, Instant now)
         {
             Guard.NotNull(field, nameof(field));
 

src/Squidex.Domain.Apps.Core.Operations/GenerateJsonSchema/JsonSchemaExtensions.cs

@@ -47,7 +47,7 @@ namespace Squidex.Domain.Apps.Core.GenerateJsonSchema
             return jsonSchema;
         }
 
-        public static JsonProperty CreateProperty(Field field)
+        public static JsonProperty CreateProperty(IField field)
         {
             var jsonProperty = new JsonProperty { IsRequired = field.RawProperties.IsRequired, Type = JsonObjectType.Object };
 

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

@@ -17,7 +17,7 @@ namespace Squidex.Domain.Apps.Core.ValidateContent
 {
     public static class FieldExtensions
     {
-        public static void AddError(this ConcurrentBag<ValidationError> errors, string message, Field field, IFieldPartitionItem partitionItem = null)
+        public static void AddError(this ConcurrentBag<ValidationError> errors, string message, IField field, IFieldPartitionItem partitionItem = null)
         {
             AddError(errors, message, !string.IsNullOrWhiteSpace(field.RawProperties.Label) ? field.RawProperties.Label : field.Name, field.Name, partitionItem);
         }
@@ -37,7 +37,7 @@ namespace Squidex.Domain.Apps.Core.ValidateContent
             errors.Add(new ValidationError(message.Replace("<FIELD>", displayName), fieldName));
         }
 
-        public static async Task ValidateAsync(this Field field, JToken value, ValidationContext context, Action<string> addError)
+        public static async Task ValidateAsync(this IField field, JToken value, ValidationContext context, Action<string> addError)
         {
             try
             {

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

@@ -23,7 +23,7 @@ namespace Squidex.Domain.Apps.Core.ValidateContent
         {
         }
 
-        public static IEnumerable<IValidator> CreateValidators(Field field)
+        public static IEnumerable<IValidator> CreateValidators(IField field)
         {
             Guard.NotNull(field, nameof(field));
 

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

@@ -33,12 +33,12 @@ namespace Squidex.Domain.Apps.Core.Operations.ValidateContent
             return validator.ValidateAsync(value, (context ?? ValidContext).Optional(true), errors.Add);
         }
 
-        public static Task ValidateAsync(this Field field, JToken value, IList<string> errors, ValidationContext context = null)
+        public static Task ValidateAsync(this IField field, JToken value, IList<string> errors, ValidationContext context = null)
         {
             return field.ValidateAsync(value, context ?? ValidContext, errors.Add);
         }
 
-        public static Task ValidateOptionalAsync(this Field field, JToken value, IList<string> errors, ValidationContext context = null)
+        public static Task ValidateOptionalAsync(this IField field, JToken value, IList<string> errors, ValidationContext context = null)
         {
             return field.ValidateAsync(value, (context ?? ValidContext).Optional(true), errors.Add);
         }