TryGetPropertyValue on a nested ComplexType returns T, should return Delta<T> #2500 (#2570)

Author: dxrdxr

src/Microsoft.AspNet.OData.Shared/DeltaOfTStructuralType.cs

@@ -92,10 +92,9 @@ public Delta(Type structuralType, IEnumerable<string> updatableProperties)
         public Delta(Type structuralType, IEnumerable<string> updatableProperties,
             PropertyInfo dynamicDictionaryPropertyInfo)
             : this(structuralType, updatableProperties: updatableProperties, dynamicDictionaryPropertyInfo, false)
-        {         
+        {
         }
 
-
         /// <summary>
         /// Initializes a new instance of <see cref="Delta{TStructuralType}"/>.
         /// </summary>
@@ -116,23 +115,18 @@ public Delta(Type structuralType, IEnumerable<string> updatableProperties,
             IsComplexType = isComplexType;
         }
 
-
-
         /// <inheritdoc/>
-        public override Type StructuredType
-            => _structuredType;
+        public override Type StructuredType => _structuredType;
 
         /// <inheritdoc/>
-        public override Type ExpectedClrType
-            => typeof(TStructuralType);
+        public override Type ExpectedClrType => typeof(TStructuralType);
 
         /// <summary>
         /// The list of property names that can be updated.
         /// </summary>
         /// <remarks>When the list is modified, any modified properties that were removed from the list are no longer
         /// considered to be changed.</remarks>
-        public IList<string> UpdatableProperties
-            => _updatableProperties;
+        public IList<string> UpdatableProperties => _updatableProperties;
 
         /// <summary>
         /// To determine if the StructuralType is a Complex type
@@ -148,9 +142,9 @@ public override void Clear()
         /// <inheritdoc/>
         public override bool TrySetPropertyValue(string name, object value)
         {
-            if (String.IsNullOrWhiteSpace(name))
+            if (string.IsNullOrWhiteSpace(name))
             {
-                throw Error.ArgumentNull("name");
+                throw Error.ArgumentNull(nameof(name));
             }
 
             if (_dynamicDictionaryPropertyinfo != null)
@@ -186,7 +180,7 @@ public override bool TryGetPropertyValue(string name, out object value)
         {
             if (name == null)
             {
-                throw Error.ArgumentNull("name");
+                throw Error.ArgumentNull(nameof(name));
             }
 
             if (_dynamicDictionaryPropertyinfo != null)
@@ -212,6 +206,9 @@ public override bool TryGetPropertyValue(string name, out object value)
                 Contract.Assert(IsDeltaOfT(deltaNestedResource.GetType()));
 
                 // Get the Delta<{NestedResourceType}>._instance using Reflection.
+                // This semantic is not correct but is preserved for backwards
+                // compatability and should be replaced in the next major release by
+                // the code in TryGetNestedPropertyValue.
                 FieldInfo field = deltaNestedResource.GetType().GetField("_instance", BindingFlags.NonPublic | BindingFlags.Instance);
                 Contract.Assert(field != null, "field != null");
                 value = field.GetValue(deltaNestedResource);
@@ -232,12 +229,48 @@ public override bool TryGetPropertyValue(string name, out object value)
             return false;
         }
 
+        /// <summary>
+        /// Attempts to get the value of the nested Property called <paramref name="name"/> from the underlying Entity.
+        /// <remarks>
+        /// Only properties that exist on Entity can be retrieved.
+        /// Only modified nested properties can be retrieved.
+        /// The nested Property type will be <see cref="IDelta"/> of its defined type.
+        /// </remarks>
+        /// </summary>
+        /// <param name="name">The name of the nested Property</param>
+        /// <param name="value">The value of the nested Property</param>
+        /// <returns><c>True</c> if the Property was found and is a nested Property</returns>
+        public bool TryGetNestedPropertyValue(string name, out object value)
+        {
+            if (name == null)
+            {
+                throw Error.ArgumentNull(nameof(name));
+            }
+
+            if (!_deltaNestedResources.ContainsKey(name))
+            {
+                value = null;
+                return false;
+            }
+
+            // This is a nested resource, the value returned must be an IDelta<T>
+            // from the dictionary of nested resources to allow the traversal of
+            // hierarchies of Delta<T>.
+            object deltaNestedResource = _deltaNestedResources[name];
+
+            Contract.Assert(deltaNestedResource != null, "deltaNestedResource != null");
+            Contract.Assert(IsDeltaOfT(deltaNestedResource.GetType()));
+
+            value = deltaNestedResource;
+            return true;
+        }
+
         /// <inheritdoc/>
         public override bool TryGetPropertyType(string name, out Type type)
         {
             if (name == null)
             {
-                throw Error.ArgumentNull("name");
+                throw Error.ArgumentNull(nameof(name));
             }
 
             if (_dynamicDictionaryPropertyinfo != null)
@@ -314,14 +347,14 @@ public void CopyChangedValues(TStructuralType original)
         {
             if (original == null)
             {
-                throw Error.ArgumentNull("original");
+                throw Error.ArgumentNull(nameof(original));
             }
 
             // Delta parameter type cannot be derived type of original
             // to prevent unrecognizable information from being applied to original resource.
             if (!_structuredType.IsAssignableFrom(original.GetType()))
             {
-                throw Error.Argument("original", SRResources.DeltaTypeMismatch, _structuredType, original.GetType());
+                throw Error.Argument(nameof(original), SRResources.DeltaTypeMismatch, _structuredType, original.GetType());
             }
 
             RuntimeHelpers.EnsureSufficientExecutionStack();
@@ -397,7 +430,7 @@ private dynamic ReAssignComplexDerivedType(TStructuralType parent, string nested
 
             //Here original type is the type for original (T) resource.
             //We will keep  going to base types and finally will get the Common Basetype for the derived complex types in to the originalType variable.
-            
+
             //The new Original type, means the new complex type (T) which will replace the current complex type.
             dynamic newOriginalNestedResource = originalValue;
 
@@ -438,12 +471,12 @@ public void CopyUnchangedValues(TStructuralType original)
         {
             if (original == null)
             {
-                throw Error.ArgumentNull("original");
+                throw Error.ArgumentNull(nameof(original));
             }
 
             if (!_structuredType.IsInstanceOfType(original))
             {
-                throw Error.Argument("original", SRResources.DeltaTypeMismatch, _structuredType, original.GetType());
+                throw Error.Argument(nameof(original), SRResources.DeltaTypeMismatch, _structuredType, original.GetType());
             }
 
             IEnumerable<PropertyAccessor<TStructuralType>> propertiesToCopy = GetUnchangedPropertyNames().Select(s => _allProperties[s]);
@@ -513,12 +546,12 @@ private static IDictionary<string, object> GetDynamicPropertyDictionary(Property
         {
             if (propertyInfo == null)
             {
-                throw Error.ArgumentNull("propertyInfo");
+                throw Error.ArgumentNull(nameof(propertyInfo));
             }
 
             if (entity == null)
             {
-                throw Error.ArgumentNull("entity");
+                throw Error.ArgumentNull(nameof(entity));
             }
 
             object propertyValue = propertyInfo.GetValue(entity);
@@ -568,7 +601,7 @@ private void Reset(Type structuralType)
         {
             if (structuralType == null)
             {
-                throw Error.ArgumentNull("structuralType");
+                throw Error.ArgumentNull(nameof(structuralType));
             }
 
             if (!typeof(TStructuralType).IsAssignableFrom(structuralType))
@@ -629,7 +662,7 @@ private bool IsIgnoredProperty(bool isTypeDataContract, PropertyInfo propertyInf
                 return !propertyInfo.GetCustomAttributes(typeof(DataMemberAttribute), inherit: true).Any();
             }
 
-            return propertyInfo.GetCustomAttributes(typeof(IgnoreDataMemberAttribute), inherit: true).Any();           
+            return propertyInfo.GetCustomAttributes(typeof(IgnoreDataMemberAttribute), inherit: true).Any();
         }
 
         // Copy changed dynamic properties and leave the unchanged dynamic properties
@@ -733,10 +766,7 @@ private void CopyUnchangedDynamicValues(TStructuralType targetEntity)
 
         private bool TrySetPropertyValueInternal(string name, object value)
         {
-            if (name == null)
-            {
-                throw Error.ArgumentNull("name");
-            }
+            Debug.Assert(name != null, "Argument name is null");
 
             if (!(_allProperties.ContainsKey(name) && _updatableProperties.Contains(name)))
             {
@@ -763,10 +793,7 @@ private bool TrySetPropertyValueInternal(string name, object value)
 
         private bool TrySetNestedResourceInternal(string name, object deltaNestedResource)
         {
-            if (name == null)
-            {
-                throw Error.ArgumentNull("name");
-            }
+            Debug.Assert(name != null, "Argument name is null");
 
             if (!(_allProperties.ContainsKey(name) && _updatableProperties.Contains(name)))
             {