-Changed empty string to be deserialized as null for nullable types

Src/Newtonsoft.Json.Tests/Converters/IsoDateTimeConverterTests.cs

@@ -236,6 +236,16 @@ namespace Newtonsoft.Json.Tests.Converters
       Assert.AreEqual("Post", c2.PostField);
     }
 
+    [Test]
+    public void NullableDeserializeEmptyString()
+    {
+      string json = @"{""DateTimeField"":""""}";
+
+      NullableDateTimeTestClass c = JsonConvert.DeserializeObject<NullableDateTimeTestClass>(json,
+        new JsonSerializerSettings { Converters = new [] {new IsoDateTimeConverter()}});
+      Assert.AreEqual(null, c.DateTimeField);
+    }
+
     [Test]
     [ExpectedException(typeof(Exception), ExpectedMessage = "Cannot convert null value to System.DateTime.")]
     public void DeserializeNullToNonNullable()

Src/Newtonsoft.Json.Tests/JsonSerializerTest.cs

@@ -2040,5 +2040,14 @@ keyword such as type of business.""
       Assert.AreEqual(2, products.Count);
       Assert.AreEqual("Product 1", products[0].Name);
     }
+
+    [Test]
+    public void DeserializeEmptyStringToNullableDateTime()
+    {
+      string json = @"{""DateTimeField"":""""}";
+
+      NullableDateTimeTestClass c = JsonConvert.DeserializeObject<NullableDateTimeTestClass>(json);
+      Assert.AreEqual(null, c.DateTimeField);
+    }
   }
 }

Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.Compact.csproj

@@ -98,6 +98,7 @@
     <Compile Include="TestObjects\MethodExecutorObject.cs" />
     <Compile Include="TestObjects\MyClass.cs" />
     <Compile Include="TestObjects\Name.cs" />
+    <Compile Include="TestObjects\NullableDateTimeTestClass.cs" />
     <Compile Include="TestObjects\PersonRaw.cs" />
     <Compile Include="TestObjects\PhoneNumber.cs" />
     <Compile Include="TestObjects\PrivateMembersClass.cs" />
@@ -127,7 +128,6 @@
     <Compile Include="Schema\JsonSchemaGeneratorTests.cs" />
     <Compile Include="Schema\JsonSchemaTests.cs" />
     <Compile Include="JsonRawTests.cs" />
-    <Compile Include="NullableDateTimeTestClass.cs" />
     <Compile Include="TestObjects\DateTimeTestClass.cs" />
     <Compile Include="Converters\IsoDateTimeConverterTests.cs" />
     <Compile Include="JsonConvertTest.cs" />

Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.Net20.csproj

@@ -102,6 +102,7 @@
     <Compile Include="TestObjects\JaggedArray.cs" />
     <Compile Include="TestObjects\MyClass.cs" />
     <Compile Include="TestObjects\Name.cs" />
+    <Compile Include="TestObjects\NullableDateTimeTestClass.cs" />
     <Compile Include="TestObjects\PersonRaw.cs" />
     <Compile Include="TestObjects\PhoneNumber.cs" />
     <Compile Include="TestObjects\PrivateMembersClass.cs" />
@@ -131,7 +132,6 @@
     <Compile Include="Schema\JsonSchemaGeneratorTests.cs" />
     <Compile Include="Schema\JsonSchemaTests.cs" />
     <Compile Include="JsonRawTests.cs" />
-    <Compile Include="NullableDateTimeTestClass.cs" />
     <Compile Include="TestObjects\DateTimeTestClass.cs" />
     <Compile Include="Converters\IsoDateTimeConverterTests.cs" />
     <Compile Include="JsonConvertTest.cs" />

Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.Silverlight.csproj

@@ -104,6 +104,7 @@
     <Compile Include="TestObjects\MethodExecutorObject.cs" />
     <Compile Include="TestObjects\MyClass.cs" />
     <Compile Include="TestObjects\Name.cs" />
+    <Compile Include="TestObjects\NullableDateTimeTestClass.cs" />
     <Compile Include="TestObjects\PersonRaw.cs" />
     <Compile Include="TestObjects\PhoneNumber.cs" />
     <Compile Include="TestObjects\PrivateMembersClass.cs" />
@@ -133,7 +134,6 @@
     <Compile Include="Schema\JsonSchemaGeneratorTests.cs" />
     <Compile Include="Schema\JsonSchemaTests.cs" />
     <Compile Include="JsonRawTests.cs" />
-    <Compile Include="NullableDateTimeTestClass.cs" />
     <Compile Include="TestObjects\DateTimeTestClass.cs" />
     <Compile Include="Converters\IsoDateTimeConverterTests.cs" />
     <Compile Include="JsonConvertTest.cs" />

Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.csproj

@@ -168,7 +168,7 @@
     <Compile Include="Schema\JsonSchemaGeneratorTests.cs" />
     <Compile Include="Schema\JsonSchemaTests.cs" />
     <Compile Include="JsonRawTests.cs" />
-    <Compile Include="NullableDateTimeTestClass.cs" />
+    <Compile Include="TestObjects\NullableDateTimeTestClass.cs" />
     <Compile Include="TestObjects\DateTimeTestClass.cs" />
     <Compile Include="Converters\IsoDateTimeConverterTests.cs" />
     <Compile Include="JsonConvertTest.cs" />

Src/Newtonsoft.Json.Tests/TestObjects/NullableDateTimeTestClass.cs

@@ -28,7 +28,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Text;
 
-namespace Newtonsoft.Json.Tests
+namespace Newtonsoft.Json.Tests.TestObjects
 {
   public class NullableDateTimeTestClass
   {

Src/Newtonsoft.Json/Converters/IsoDateTimeConverter.cs

@@ -94,7 +94,8 @@ namespace Newtonsoft.Json.Converters
     /// <returns>The object value.</returns>
     public override object ReadJson(JsonReader reader, Type objectType, JsonSerializer serializer)
     {
-      Type t = (ReflectionUtils.IsNullableType(objectType))
+      bool nullable = ReflectionUtils.IsNullableType(objectType);
+      Type t = (nullable)
         ? Nullable.GetUnderlyingType(objectType)
         : objectType;
 
@@ -111,6 +112,9 @@ namespace Newtonsoft.Json.Converters
 
       string dateText = reader.Value.ToString();
 
+      if (string.IsNullOrEmpty(dateText) && nullable)
+        return null;
+
       if (t == typeof(DateTimeOffset))
       {
         if (!string.IsNullOrEmpty(_dateTimeFormat))

Src/Newtonsoft.Json/Serialization/JsonSerializerReader.cs

@@ -169,6 +169,13 @@ namespace Newtonsoft.Json.Serialization
           case JsonToken.String:
           case JsonToken.Boolean:
           case JsonToken.Date:
+            // convert empty string to null automatically
+            if (reader.Value is string &&
+              string.IsNullOrEmpty((string)reader.Value) &&
+              objectType != null &&
+              ReflectionUtils.IsNullable(objectType))
+              return null;
+
             return EnsureType(reader.Value, objectType);
           case JsonToken.StartConstructor:
           case JsonToken.EndConstructor: