PropertyGrid: added ability to define editors with a simple attribute called TypeEditorAttirbute. You can use a default editor or create a custom editor as follows:

public class MyCustomEditor : ITypeEditor
    {
        public FrameworkElement ResolveEditor(PropertyItem propertyItem)
        {
            TextBox editor = new TextBox();
            Binding binding = new Binding("Value"); //bind to the Value property of the PropertyItem instance
            binding.Source = propertyItem;
            binding.Mode = propertyItem.IsWriteable ? BindingMode.TwoWay : BindingMode.OneWay;
            BindingOperations.SetBinding(editor, TextBox.TextProperty, binding);
            return editor;
        }
    }

Then attribute the property to use the editor on:

        private TimeSpan _timeSpan;
        [TypeEditor(typeof(MyCustomEditor))]
        public TimeSpan TimeSpan
        {
            get { return _timeSpan; }
            set { _timeSpan = value; }
        }

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/PropertyGrid/Implementation/Attributes/TypeEditorAttribute.cs

@@ -0,0 +1,18 @@
+using System;
+
+namespace Microsoft.Windows.Controls.PropertyGrid.Attributes
+{
+    public class TypeEditorAttribute : Attribute
+    {
+        public Type Type { get; set; }
+
+        public TypeEditorAttribute(Type type)
+        {
+            var valueSourceInterface = type.GetInterface("Microsoft.Windows.Controls.PropertyGrid.Editors.ITypeEditor");
+            if (valueSourceInterface == null)
+                throw new ArgumentException("Type must implement the ITypeEditor interface.", "type");
+
+            Type = type;
+        }
+    }
+}

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/PropertyGrid/Implementation/PropertyGrid.cs

@@ -414,7 +414,7 @@ namespace Microsoft.Windows.Controls.PropertyGrid
 
         private FrameworkElement GetTypeEditor(PropertyItem propertyItem)
         {
-            //first check for any attribute editor
+            //first check for an attribute editor
             FrameworkElement editor = GetAttibuteEditor(propertyItem);
 
             //now look for a custom editor based on editor definitions
@@ -432,9 +432,16 @@ namespace Microsoft.Windows.Controls.PropertyGrid
         {
             FrameworkElement editor = null;
 
-            var attribute = GetAttribute<ItemsSourceAttribute>(propertyItem.PropertyDescriptor);
+            var itemsSourceAttribute = GetAttribute<ItemsSourceAttribute>(propertyItem.PropertyDescriptor);
-            if (attribute != null)
+            if (itemsSourceAttribute != null)
-                editor = new ItemsSourceEditor(attribute).ResolveEditor(propertyItem);
+                editor = new ItemsSourceEditor(itemsSourceAttribute).ResolveEditor(propertyItem);
+
+            var editorAttribute = GetAttribute<TypeEditorAttribute>(propertyItem.PropertyDescriptor);
+            if (editorAttribute != null)
+            {
+                var instance = Activator.CreateInstance(editorAttribute.Type);
+                editor = (instance as ITypeEditor).ResolveEditor(propertyItem);
+            }
 
             return editor;
         }

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/WPFToolkit.Extended.csproj

@@ -237,6 +237,7 @@
       <DesignTimeSharedInput>True</DesignTimeSharedInput>
     </Compile>
     <Compile Include="BusyIndicator\Implementation\VisualStates.BusyIndicator.cs" />
+    <Compile Include="PropertyGrid\Implementation\Attributes\TypeEditorAttribute.cs" />
     <Compile Include="PropertyGrid\Implementation\Attributes\IItemsSource.cs" />
     <Compile Include="PropertyGrid\Implementation\Attributes\ItemsSourceAttribute.cs" />
     <Compile Include="PropertyGrid\Implementation\Commands\PropertyGridCommands.cs" />