support for .NET framework 3.5

Still have bugs

Net35/HandyControl_Net35/Shell/Standard/SafeFindHandle.cs

@@ -0,0 +1,20 @@
+namespace Standard
+{
+    using Microsoft.Win32.SafeHandles;
+    using System;
+    using System.Security.Permissions;
+
+    internal sealed class SafeFindHandle : SafeHandleZeroOrMinusOneIsInvalid
+    {
+        [SecurityPermission(SecurityAction.LinkDemand, UnmanagedCode=true)]
+        private SafeFindHandle() : base(true)
+        {
+        }
+
+        protected override bool ReleaseHandle()
+        {
+            return Standard.NativeMethods.FindClose(base.handle);
+        }
+    }
+}
+