Add support for nullable types

src/JSONParser.cs

@@ -128,9 +128,13 @@ static List<string> Split(string json)
         internal static object ParseValue(Type type, string json)
         {
             if (type == typeof(string))
-            {
+            {
+                if (json == "null")
+                    return null;
+
                 if (json.Length <= 2)
                     return string.Empty;
+
                 StringBuilder parseStringBuilder = new StringBuilder(json.Length);
                 for (int i = 1; i < json.Length - 1; ++i)
                 {
@@ -198,6 +202,11 @@ internal static object ParseValue(Type type, string json)
                     newArray.SetValue(ParseValue(arrayType, elems[i]), i);
                 splitArrayPool.Push(elems);
                 return newArray;
+            }
+            if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>))
+            {
+                Type underlyingType = type.GetGenericArguments()[0];
+                return ParseValue(underlyingType, json);
             }
             if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(List<>))
             {

test/TestParser.cs

@@ -439,5 +439,57 @@ public void TestDuplicateKeysInAnonymousObject()
              */
             Assert.AreEqual(dictionary["hello"], "hell", "The parser stored an incorrect value for the duplicated key");
         }
+
+        private class SimpleModelWithNulls
+        {
+            public string AString { get; set; }
+            public int? NullableInt { get; set; }
+            public float? NullableFloat { get; set; }
+        }
+
+        [TestMethod]
+        public void FromJson_NullString_IsParsedCorrectly()
+        {
+            // Arrange
+            var json = "{\"AString\": null}";
+
+            // Act
+            var actual = json.FromJson<SimpleModelWithNulls>();
+
+            // Assert
+            Assert.IsNull(actual.AString);
+        }
+
+        [DataTestMethod]
+        [DataRow(null)]
+        [DataRow(5)]
+        [DataRow(-1)]
+        public void FromJson_NullableInt_IsParsedCorrectly(int? value)
+        {
+            // Arrange
+            var json = "{\"NullableInt\": " + (value?.ToString() ?? "null") + "}";
+
+            // Act
+            var actual = json.FromJson<SimpleModelWithNulls>();
+
+            // Assert
+            Assert.AreEqual(value, actual.NullableInt);
+        }
+
+        [DataTestMethod]
+        [DataRow(null)]
+        [DataRow(3.0f)]
+        [DataRow(2.5f)]
+        public void FromJson_NullableFloat_IsParsedCorrectly(float? value)
+        {
+            // Arrange
+            var json = "{\"NullableFloat\": " + (value?.ToString(System.Globalization.CultureInfo.InvariantCulture) ?? "null") + "}";
+
+            // Act
+            var actual = json.FromJson<SimpleModelWithNulls>();
+
+            // Assert
+            Assert.AreEqual(value, actual.NullableFloat);
+        }
     }
 }