add dictionary extension methods

Blarg.GameFramework/Blarg.GameFramework.csproj

@@ -159,6 +159,7 @@
     <Compile Include="Graphics\ScreenEffects\FlashEffect.cs" />
     <Compile Include="IService.cs" />
     <Compile Include="ServiceContainer.cs" />
+    <Compile Include="Support\DictionaryExtensions.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath32)\Microsoft\Portable\$(TargetFrameworkVersion)\Microsoft.Portable.CSharp.targets" />
   <ItemGroup>

Blarg.GameFramework/ServiceContainer.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using Blarg.GameFramework.Support;
 
 namespace Blarg.GameFramework
 {
@@ -22,7 +23,6 @@ namespace Blarg.GameFramework
 			var type = service.GetType();
 			if (type.IsValueType)
 				throw new ArgumentException("ServiceContainer cannot be used with value types.", "service");
-
 			if (_services.ContainsKey(type))
 				throw new InvalidOperationException("Service object of this type has already been registered.");
 
@@ -41,18 +41,15 @@ namespace Blarg.GameFramework
 			if (type.IsValueType)
 				throw new ArgumentException("ServiceContainer cannot be used with value types.", "service");
 
-			object registeredService;
-			_services.TryGetValue(type, out registeredService);
+			var registeredService = _services.Get(type);
 			if (registeredService == null)
 				return;
-
 			if (registeredService != service)
 				throw new InvalidOperationException("This is not the service object that was registered under this type.");
 
 			_services.Remove(type);
 			Platform.Logger.Debug(LOG_TAG, "Unregistered object of type {0}.", type);
 
-
 			if (registeredService is IService)
 				((IService)registeredService).OnUnregister();
 		}
@@ -67,10 +64,8 @@ namespace Blarg.GameFramework
 		{
 			if (type.IsValueType)
 				throw new ArgumentException("ServiceContainer cannot be used with value types.", "type");
-
-			object service;
-			_services.TryGetValue(type, out service);
-			return service;
+			else
+				return _services.Get(type);
 		}
 
 		public void Dispose()

Blarg.GameFramework/Support/DictionaryExtensions.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+
+namespace Blarg.GameFramework.Support
+{
+	public static class DictionaryExtensions
+	{
+		public static TValue Get<TKey, TValue>(this IDictionary<TKey, TValue> dict, TKey key) where TValue : class
+		{
+			TValue result;
+			dict.TryGetValue(key, out result);
+			return result;
+		}
+	}
+}
+