Fix for UIRequest.Icon deserialization exception due to nullable stru…

…ct types.

Fixes Trac #195

src/DotNetOpenAuth.Test/Messaging/Reflection/MessagePartTests.cs

@@ -28,7 +28,12 @@ public void RequiredNonNullableStruct() {
 
 		[TestCase]
 		public void OptionalNullableStruct() {
-			this.ParameterizedMessageTypeTest(typeof(MessageWithNullableOptionalStruct));
+			var message = new MessageWithNullableOptionalStruct();
+			var part = this.ParameterizedMessageTypeTest(message.GetType());
+
+			Assert.IsNull(part.GetValue(message));
+			part.SetValue(message, "3");
+			Assert.AreEqual("3", part.GetValue(message));
 		}
 
 		[TestCase]

src/DotNetOpenAuth.Test/OpenId/Extensions/UI/UIRequestTests.cs

@@ -14,10 +14,27 @@ namespace DotNetOpenAuth.Test.OpenId.Extensions.UI {
 	public class UIRequestTests : OpenIdTestBase {
 		[TestCase]
 		public void Defaults() {
-			UIRequest request = new UIRequest();
+			var request = new UIRequest();
 			Assert.AreEqual("popup", request.Mode);
 			Assert.AreEqual(1, request.LanguagePreference.Length);
 			Assert.AreEqual(CultureInfo.CurrentUICulture, request.LanguagePreference[0]);
+			Assert.IsFalse(request.Icon.HasValue);
+		}
+
+		[TestCase]
+		public void IconEncodingDecoding()
+		{
+			var request = new UIRequest();
+			MessageDictionary dictionary = this.MessageDescriptions.GetAccessor(request);
+			Assert.IsFalse(dictionary.ContainsKey("icon"));
+
+			Assert.IsFalse(request.Icon.HasValue);
+			dictionary["icon"] = "true";
+			Assert.IsTrue(request.Icon.Value);
+
+			dictionary.ClearValues();
+			request.Icon = true;
+			Assert.AreEqual("true", dictionary["icon"]);
 		}
 
 		[TestCase]

src/DotNetOpenAuth/Messaging/Reflection/MessagePart.cs

@@ -129,9 +129,25 @@ internal MessagePart(MemberInfo member, MessagePartAttribute attribute) {
 			Contract.Assume(this.memberDeclaredType != null); // CC missing PropertyInfo.PropertyType ensures result != null
 			if (attribute.Encoder == null) {
 				if (!converters.TryGetValue(this.memberDeclaredType, out this.converter)) {
-					this.converter = new ValueMapping(
-						obj => obj != null ? obj.ToString() : null,
-						str => str != null ? Convert.ChangeType(str, this.memberDeclaredType, CultureInfo.InvariantCulture) : null);
+					if (this.memberDeclaredType.IsGenericType &&
+						this.memberDeclaredType.GetGenericTypeDefinition() == typeof(Nullable<>)) {
+						// It's a nullable type.  Try again to look up an appropriate converter for the underlying type.
+						Type underlyingType = Nullable.GetUnderlyingType(this.memberDeclaredType);
+						ValueMapping underlyingMapping;
+						if (converters.TryGetValue(underlyingType, out underlyingMapping)) {
+							this.converter = new ValueMapping(
+								underlyingMapping.ValueToString,
+								str => str != null ? underlyingMapping.StringToValue(str) : null);
+						} else {
+							this.converter = new ValueMapping(
+								obj => obj != null ? obj.ToString() : null,
+								str => str != null ? Convert.ChangeType(str, underlyingType, CultureInfo.InvariantCulture) : null);
+						}
+					} else {
+						this.converter = new ValueMapping(
+							obj => obj != null ? obj.ToString() : null,
+							str => str != null ? Convert.ChangeType(str, this.memberDeclaredType, CultureInfo.InvariantCulture) : null);
+					}
 				}
 			} else {
 				this.converter = new ValueMapping(GetEncoder(attribute.Encoder));
@@ -252,7 +268,7 @@ private static object DeriveDefaultValue(Type type) {
 		}
 
 		/// <summary>
-		/// Adds a pair of type conversion functions to the static converstion map.
+		/// Adds a pair of type conversion functions to the static conversion map.
 		/// </summary>
 		/// <typeparam name="T">The custom type to convert to and from strings.</typeparam>
 		/// <param name="toString">The function to convert the custom type to a string.</param>