Merge pull request #98 from github/shana/uiprovider-caching

Caching the UIProvider

Author: haacked

src/GitHub.Exports/Extensions/VSExtensions.cs

@@ -7,21 +7,26 @@ namespace GitHub.Extensions
 {
     public static class VSExtensions
     {
+        static IUIProvider cachedUIProvider = null;
+
         public static T TryGetService<T>(this IServiceProvider serviceProvider) where T : class
         {
             return serviceProvider.TryGetService(typeof(T)) as T;
         }
 
         public static object TryGetService(this IServiceProvider serviceProvider, Type type)
         {
+            if (cachedUIProvider != null && type == typeof(IUIProvider))
+                return cachedUIProvider;
+
             var ui = serviceProvider as IUIProvider;
             if (ui != null)
                 return ui.TryGetService(type);
             else
             {
                 try
                 {
-                    return serviceProvider.GetService(type);
+                    return GetServiceAndCache(serviceProvider, type, ref cachedUIProvider);
                 }
                 catch (Exception ex)
                 {
@@ -33,20 +38,42 @@ public static object TryGetService(this IServiceProvider serviceProvider, Type t
 
         public static T GetService<T>(this IServiceProvider serviceProvider)
         {
-            return (T)serviceProvider.GetService(typeof(T));
+            if (cachedUIProvider != null && typeof(T) == typeof(IUIProvider))
+                return (T)cachedUIProvider;
+
+            return (T)GetServiceAndCache(serviceProvider, typeof(T), ref cachedUIProvider);
         }
 
         public static T GetExportedValue<T>(this IServiceProvider serviceProvider)
         {
+            if (cachedUIProvider != null && typeof(T) == typeof(IUIProvider))
+                return (T)cachedUIProvider;
+
             var ui = serviceProvider as IUIProvider;
             return ui != null
                 ? ui.GetService<T>()
-                : VisualStudio.Services.ComponentModel.DefaultExportProvider.GetExportedValue<T>();
+                : GetExportedValueAndCache<T, IUIProvider>(ref cachedUIProvider);
         }
 
         public static ITeamExplorerSection GetSection(this IServiceProvider serviceProvider, Guid section)
         {
             return serviceProvider?.GetService<ITeamExplorerPage>()?.GetSection(section);
         }
+
+        static object GetServiceAndCache<CacheType>(IServiceProvider provider, Type type, ref CacheType cache)
+        {
+            var ret = provider.GetService(type);
+            if (type == typeof(CacheType))
+                cache = (CacheType)ret;
+            return ret;
+        }
+
+        static T GetExportedValueAndCache<T, CacheType>(ref CacheType cache)
+        {
+            var ret = VisualStudio.Services.ComponentModel.DefaultExportProvider.GetExportedValue<T>();
+            if (typeof(T) == typeof(CacheType))
+                cache = (CacheType)(object)ret;
+            return ret;
+        }
     }
 }