ExtensibleObject should set default values for defined properties.

framework/src/Volo.Abp.Core/Volo/Abp/Reflection/TypeHelper.cs

@@ -131,5 +131,20 @@ namespace Volo.Abp.Reflection
                    type == typeof(TimeSpan) ||
                    type == typeof(Guid);
         }
+
+        public static object GetDefaultValue<T>()
+        {
+            return GetDefaultValue(typeof(T));
+        }
+
+        public static object GetDefaultValue(Type type)
+        {
+            if (type.IsValueType)
+            {
+                return Activator.CreateInstance(type);
+            }
+
+            return null;
+        }
     }
 }

framework/src/Volo.Abp.Ddd.Domain/Volo/Abp/Domain/Entities/AggregateRoot.cs

@@ -25,8 +25,9 @@ namespace Volo.Abp.Domain.Entities
 
         protected AggregateRoot()
         {
-            ExtraProperties = new Dictionary<string, object>();
             ConcurrencyStamp = Guid.NewGuid().ToString("N");
+            ExtraProperties = new Dictionary<string, object>();
+            this.SetDefaultsForExtraProperties();
         }
 
         protected virtual void AddLocalEvent(object eventData)
@@ -85,15 +86,17 @@ namespace Volo.Abp.Domain.Entities
 
         protected AggregateRoot()
         {
-            ExtraProperties = new Dictionary<string, object>();
             ConcurrencyStamp = Guid.NewGuid().ToString("N");
+            ExtraProperties = new Dictionary<string, object>();
+            this.SetDefaultsForExtraProperties();
         }
 
         protected AggregateRoot(TKey id)
             : base(id)
         {
-            ExtraProperties = new Dictionary<string, object>();
             ConcurrencyStamp = Guid.NewGuid().ToString("N");
+            ExtraProperties = new Dictionary<string, object>();
+            this.SetDefaultsForExtraProperties();
         }
 
         protected virtual void AddLocalEvent(object eventData)

framework/src/Volo.Abp.ObjectExtending/Volo/Abp/Data/HasExtraPropertiesExtensions.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Globalization;
+using Volo.Abp.ObjectExtending;
 using Volo.Abp.Reflection;
 
 namespace Volo.Abp.Data
@@ -49,5 +50,34 @@ namespace Volo.Abp.Data
             source.ExtraProperties.Remove(name);
             return source;
         }
+
+        public static TSource SetDefaultsForExtraProperties<TSource>(this TSource source, Type objectType = null)
+            where TSource : IHasExtraProperties
+        {
+            var properties = ObjectExtensionManager.Instance
+                .GetProperties(objectType ?? typeof(TSource));
+
+            foreach (var property in properties)
+            {
+                if (source.HasProperty(property.Name))
+                {
+                    continue;
+                }
+
+                source.ExtraProperties[property.Name] = TypeHelper.GetDefaultValue(property.Type);
+            }
+
+            return source;
+        }
+
+        public static void SetDefaultsForExtraProperties(object source, Type objectType)
+        {
+            if (!(source is IHasExtraProperties))
+            {
+                throw new ArgumentException($"Given {nameof(source)} object does not implement the {nameof(IHasExtraProperties)} interface!", nameof(source));
+            }
+
+            ((IHasExtraProperties) source).SetDefaultsForExtraProperties(objectType);
+        }
     }
 }

framework/src/Volo.Abp.ObjectExtending/Volo/Abp/ObjectExtending/ExtensibleObject.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
 using Volo.Abp.Data;
+using Volo.Abp.DynamicProxy;
 
 namespace Volo.Abp.ObjectExtending
 {
@@ -11,8 +12,19 @@ namespace Volo.Abp.ObjectExtending
         public Dictionary<string, object> ExtraProperties { get; protected set; }
 
         public ExtensibleObject()
+            : this(true)
+        {
+
+        }
+
+        public ExtensibleObject(bool setDefaultsForExtraProperties)
         {
             ExtraProperties = new Dictionary<string, object>();
+
+            if (setDefaultsForExtraProperties)
+            {
+                this.SetDefaultsForExtraProperties(ProxyHelper.UnProxy(this).GetType());
+            }
         }
 
         public virtual IEnumerable<ValidationResult> Validate(ValidationContext validationContext)

framework/test/Volo.Abp.ObjectExtending.Tests/Volo/Abp/ObjectExtending/ExtensibleObject_Tests.cs

@@ -0,0 +1,37 @@
+using Shouldly;
+using Volo.Abp.Data;
+using Volo.Abp.ObjectExtending.TestObjects;
+using Xunit;
+
+namespace Volo.Abp.ObjectExtending
+{
+    public class ExtensibleObject_Tests : AbpObjectExtendingTestBase
+    {
+        [Fact]
+        public void Should_Set_Default_Values_For_Defined_Properties_On_Create()
+        {
+            var person = new ExtensibleTestPerson();
+
+            person.HasProperty("Name").ShouldBeTrue();
+            person.HasProperty("Age").ShouldBeTrue();
+            person.HasProperty("NoPairCheck").ShouldBeTrue();
+            person.HasProperty("CityName").ShouldBeTrue();
+
+            person.GetProperty<string>("Name").ShouldBeNull();
+            person.GetProperty<int>("Age").ShouldBe(0);
+            person.GetProperty<string>("NoPairCheck").ShouldBeNull();
+            person.GetProperty<string>("CityName").ShouldBeNull();
+        }
+
+        [Fact]
+        public void Should_Not_Set_Default_Values_For_Defined_Properties_If_Requested()
+        {
+            var person = new ExtensibleTestPerson(false);
+
+            person.HasProperty("Name").ShouldBeFalse();
+            person.HasProperty("Age").ShouldBeFalse();
+            person.HasProperty("NoPairCheck").ShouldBeFalse();
+            person.HasProperty("CityName").ShouldBeFalse();
+        }
+    }
+}

framework/test/Volo.Abp.ObjectExtending.Tests/Volo/Abp/ObjectExtending/TestObjects/ExtensibleTestPerson.cs

@@ -2,6 +2,15 @@
 {
     public class ExtensibleTestPerson : ExtensibleObject
     {
+        public ExtensibleTestPerson()
+        {
 
+        }
+
+        public ExtensibleTestPerson(bool setDefaultsForExtraProperties)
+            : base(setDefaultsForExtraProperties)
+        {
+
+        }
     }
 }