Fix WinForms designer not resolving OxyPlot assembly.

With an OxyPlot.WindowsForms.PlotView on the form on re-opening the
form in the designer you would see the following error message and
the form would not be displayed:

   Could not find type 'OxyPlot.WindowsForms.PlotView'

The PlotView type was being resolved correctly by the
TypeResolutionService to the OxyPlot.WindowsForms assembly but
getting the type required OxyPlot.dll to be resolved which was
not being done.

Fixes #713

src/Main/Base/Project/Designer/TypeResolutionService.cs

@@ -411,9 +411,11 @@ public Type GetType(string name, bool throwOnError, bool ignoreCase)
 						ITypeDefinition definition = ReflectionHelper.ParseReflectionName(name)
 							.Resolve(compilation).GetDefinition();
 						if (definition != null) {
-							Assembly assembly = LoadAssembly(definition.ParentAssembly);
-							if (assembly != null) {
-								type = assembly.GetType(name, false, ignoreCase);
+							using (var resolver = new ProjectAssemblyResolver(compilation, this)) {
+								Assembly assembly = LoadAssembly(definition.ParentAssembly);
+								if (assembly != null) {
+									type = assembly.GetType(name, false, ignoreCase);
+								}
 							}
 						}
 					}
@@ -582,5 +584,37 @@ static Assembly AssemblyResolveEventHandler(object sender, ResolveEventArgs args
 			}
 			return lastAssembly;
 		}
+
+		class ProjectAssemblyResolver : IDisposable
+		{
+			readonly ICompilation compilation;
+			readonly TypeResolutionService typeResolutionService;
+
+			public ProjectAssemblyResolver(ICompilation compilation, TypeResolutionService typeResolutionService)
+			{
+				this.compilation = compilation;
+				this.typeResolutionService = typeResolutionService;
+				AppDomain.CurrentDomain.AssemblyResolve += AssemblyResolve;
+			}
+
+			public void Dispose()
+			{
+				AppDomain.CurrentDomain.AssemblyResolve -= AssemblyResolve;
+			}
+
+			Assembly AssemblyResolve(object sender, ResolveEventArgs args)
+			{
+				try {
+					IAssembly assembly = compilation.Assemblies
+						.FirstOrDefault(asm => asm.FullAssemblyName == args.Name);
+					if (assembly != null) {
+						return typeResolutionService.LoadAssembly(assembly);
+					}
+				} catch (Exception ex) {
+					LoggingService.Error(ex);
+				}
+				return null;
+			}
+		}
 	}
 }