misc optimization & refactoring

Backup/HyperTypeDescriptionProvider.cs

@@ -0,0 +1,74 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.ComponentModel;
+using System.Security.Permissions;
+
+/* Change history:
+ * 20 Apr 2007  Marc Gravell    Rollback dictionary on error;
+ *                              Assert ReflectionPermission for main creation
+ *                                  (thanks/credit to Josh Smith for feedback/hints)
+ */
+
+namespace Hyper.ComponentModel {
+    public sealed class HyperTypeDescriptionProvider : TypeDescriptionProvider {
+        public static void Add(Type type) {
+            TypeDescriptionProvider parent = TypeDescriptor.GetProvider(type);
+            TypeDescriptor.AddProvider(new HyperTypeDescriptionProvider(parent), type);
+        }
+        public HyperTypeDescriptionProvider() : this(typeof(object)) { }
+        public HyperTypeDescriptionProvider(Type type) : this(TypeDescriptor.GetProvider(type)) { }
+        public HyperTypeDescriptionProvider(TypeDescriptionProvider parent) : base(parent) { }
+        public static void Clear(Type type) {
+            lock (descriptors) {
+                descriptors.Remove(type);
+            }
+        }
+        public static void Clear() {
+            lock (descriptors) {
+                descriptors.Clear();
+            }
+        }
+        private static readonly Dictionary<Type, ICustomTypeDescriptor> descriptors = new Dictionary<Type, ICustomTypeDescriptor>();
+        public sealed override ICustomTypeDescriptor GetTypeDescriptor(Type objectType, object instance) {
+            ICustomTypeDescriptor descriptor;
+            lock (descriptors) {
+                if (!descriptors.TryGetValue(objectType, out descriptor)) {
+                    try
+                    {
+                        descriptor = BuildDescriptor(objectType);
+                    }
+                    catch
+                    {
+                        return base.GetTypeDescriptor(objectType, instance);
+                    }
+                }
+                return descriptor;
+            }
+        }
+        [ReflectionPermission( SecurityAction.Assert, Flags = ReflectionPermissionFlag.AllFlags)]
+        private ICustomTypeDescriptor BuildDescriptor(Type objectType)
+        {
+            // NOTE: "descriptors" already locked here
+
+            // get the parent descriptor and add to the dictionary so that
+            // building the new descriptor will use the base rather than recursing
+            ICustomTypeDescriptor descriptor = base.GetTypeDescriptor(objectType, null);
+            descriptors.Add(objectType, descriptor);
+            try
+            {
+                // build a new descriptor from this, and replace the lookup
+                descriptor = new HyperTypeDescriptor(descriptor);
+                descriptors[objectType] = descriptor;
+                return descriptor;
+            }
+            catch
+            {   // rollback and throw
+                // (perhaps because the specific caller lacked permissions;
+                // another caller may be successful)
+                descriptors.Remove(objectType);
+                throw;
+            }
+        }
+    }
+}