HasFlag doesn't exist in NET 3.5

GongSolutions.Wpf.DragDrop/DropTargetInsertionAdorner.cs

@@ -1,13 +1,10 @@
 using System;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using System.Linq;
-using System.Text;
 using System.Windows;
-using System.Windows.Data;
 using System.Windows.Media;
 using System.Windows.Controls;
-using System.Collections;
+#if NET35
+using GongSolutions.Wpf.DragDrop.Utilities;
+#endif
 
 namespace GongSolutions.Wpf.DragDrop
 {

GongSolutions.Wpf.DragDrop/Utilities/TypeUtilities.cs

@@ -1,14 +1,38 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Text;
 using System.Collections;
-using System.Reflection;
 
 namespace GongSolutions.Wpf.DragDrop.Utilities
 {
-  public class TypeUtilities
+  public static class TypeUtilities
   {
+#if NET35
+    /// <summary>
+    /// Check to see if a flags enumeration has a specific flag set.
+    /// </summary>
+    /// <param name="variable">Flags enumeration to check</param>
+    /// <param name="flag"></param>
+    public static bool HasFlag(this Enum variable, Enum flag)
+    {
+      if (variable == null) {
+        return false;
+      }
+
+      if (flag == null) {
+        throw new ArgumentNullException("flag");
+      }
+
+      if (flag.GetType() != variable.GetType()) {
+        throw new ArgumentException(string.Format("Enumeration type mismatch.  The flag is of type '{0}', was expecting '{1}'.", flag.GetType(), variable.GetType()));
+      }
+
+      var uFlag = Convert.ToUInt64(flag);
+      var uVar = Convert.ToUInt64(variable);
+      return ((uVar & uFlag) == uFlag);
+    }
+#endif
+
     public static IEnumerable CreateDynamicallyTypedList(IEnumerable source)
     {
       var type = GetCommonBaseClass(source);