-Fixed roundtripping double.MaxValue and float.MaxValue as dictionary keys

Src/Newtonsoft.Json.Tests/Serialization/JsonSerializerCollectionsTests.cs

@@ -63,6 +63,39 @@ namespace Newtonsoft.Json.Tests.Serialization
     [TestFixture]
     public class JsonSerializerCollectionsTests : TestFixtureBase
     {
+        [Test]
+        public void DoubleKey_WholeValue()
+        {
+            Dictionary<double, int> dictionary = new Dictionary<double, int> { { 1d, 1 } };
+            string output = JsonConvert.SerializeObject(dictionary);
+            Assert.AreEqual(@"{""1"":1}", output);
+
+            Dictionary<double, int> deserializedValue = JsonConvert.DeserializeObject<Dictionary<double, int>>(output);
+            Assert.AreEqual(1d, deserializedValue.First().Key);
+        }
+
+        [Test]
+        public void DoubleKey_MaxValue()
+        {
+            Dictionary<double, int> dictionary = new Dictionary<double, int> { { double.MaxValue, 1 } };
+            string output = JsonConvert.SerializeObject(dictionary);
+            Assert.AreEqual(@"{""1.7976931348623157E+308"":1}", output);
+
+            Dictionary<double, int> deserializedValue = JsonConvert.DeserializeObject<Dictionary<double, int>>(output);
+            Assert.AreEqual(double.MaxValue, deserializedValue.First().Key);
+        }
+
+        [Test]
+        public void FloatKey_MaxValue()
+        {
+            Dictionary<float, int> dictionary = new Dictionary<float, int> { { float.MaxValue, 1 } };
+            string output = JsonConvert.SerializeObject(dictionary);
+            Assert.AreEqual(@"{""3.40282347E+38"":1}", output);
+
+            Dictionary<float, int> deserializedValue = JsonConvert.DeserializeObject<Dictionary<float, int>>(output);
+            Assert.AreEqual(float.MaxValue, deserializedValue.First().Key);
+        }
+
         public class TestCollectionPrivateParameterized : IEnumerable<int>
         {
             private readonly List<int> _bars;

Src/Newtonsoft.Json/Serialization/JsonSerializerInternalWriter.cs

@@ -1130,28 +1130,49 @@ namespace Newtonsoft.Json.Serialization
             if (contract.ContractType == JsonContractType.Primitive)
             {
                 JsonPrimitiveContract primitiveContract = (JsonPrimitiveContract)contract;
-                if (primitiveContract.TypeCode == PrimitiveTypeCode.DateTime || primitiveContract.TypeCode == PrimitiveTypeCode.DateTimeNullable)
+                switch (primitiveContract.TypeCode)
                 {
-                    DateTime dt = DateTimeUtils.EnsureDateTime((DateTime)name, writer.DateTimeZoneHandling);
+                    case PrimitiveTypeCode.DateTime:
+                    case PrimitiveTypeCode.DateTimeNullable:
+                    {
+                        DateTime dt = DateTimeUtils.EnsureDateTime((DateTime)name, writer.DateTimeZoneHandling);
 
-                    escape = false;
-                    StringWriter sw = new StringWriter(CultureInfo.InvariantCulture);
-                    DateTimeUtils.WriteDateTimeString(sw, dt, writer.DateFormatHandling, writer.DateFormatString, writer.Culture);
-                    return sw.ToString();
-                }
+                        escape = false;
+                        StringWriter sw = new StringWriter(CultureInfo.InvariantCulture);
+                        DateTimeUtils.WriteDateTimeString(sw, dt, writer.DateFormatHandling, writer.DateFormatString, writer.Culture);
+                        return sw.ToString();
+                    }
 #if !NET20
-                else if (primitiveContract.TypeCode == PrimitiveTypeCode.DateTimeOffset || primitiveContract.TypeCode == PrimitiveTypeCode.DateTimeOffsetNullable)
-                {
-                    escape = false;
-                    StringWriter sw = new StringWriter(CultureInfo.InvariantCulture);
-                    DateTimeUtils.WriteDateTimeOffsetString(sw, (DateTimeOffset)name, writer.DateFormatHandling, writer.DateFormatString, writer.Culture);
-                    return sw.ToString();
-                }
+                    case PrimitiveTypeCode.DateTimeOffset:
+                    case PrimitiveTypeCode.DateTimeOffsetNullable:
+                    {
+                        escape = false;
+                        StringWriter sw = new StringWriter(CultureInfo.InvariantCulture);
+                        DateTimeUtils.WriteDateTimeOffsetString(sw, (DateTimeOffset)name, writer.DateFormatHandling, writer.DateFormatString, writer.Culture);
+                        return sw.ToString();
+                    }
 #endif
-                else
-                {
-                    escape = true;
-                    return Convert.ToString(name, CultureInfo.InvariantCulture);
+                    case PrimitiveTypeCode.Double:
+                    case PrimitiveTypeCode.DoubleNullable:
+                    {
+                        double d = (double)name;
+
+                        escape = false;
+                        return d.ToString("R", CultureInfo.InvariantCulture);
+                    }
+                    case PrimitiveTypeCode.Single:
+                    case PrimitiveTypeCode.SingleNullable:
+                    {
+                        float f = (float)name;
+
+                        escape = false;
+                        return f.ToString("R", CultureInfo.InvariantCulture);
+                    }
+                    default:
+                    {
+                        escape = true;
+                        return Convert.ToString(name, CultureInfo.InvariantCulture);
+                    }
                 }
             }
             else if (TryConvertToString(name, name.GetType(), out propertyName))