Reset new dialog properties

Author: miloush

src/Microsoft.DotNet.Wpf/src/PresentationFramework/Microsoft/Win32/CommonItemDialog.cs

@@ -562,9 +562,12 @@ private void Initialize()
             _itemNames = null;
             _title.Value = null;
             _initialDirectory.Value = null;
+            _defaultDirectory.Value = null;
+            _rootDirectory.Value = null;
 
             // Set this to an empty list so callers can simply add to it.  They can also replace it wholesale.
             CustomPlaces = new List<FileDialogCustomPlace>();
+            ClientGuid = null;
         }
 
         private bool HandleItemOk(IFileDialog dialog)

src/Microsoft.DotNet.Wpf/src/PresentationFramework/Microsoft/Win32/OpenFileDialog.cs

@@ -205,17 +205,7 @@ public bool Multiselect
         /// Gets or sets a value indicating whether the dialog 
         /// contains a read-only check box.  
         /// </summary>
-        public bool ShowReadOnly
-        {
-            get
-            {
-                return _showReadOnly;
-            }
-            set
-            {
-                _showReadOnly = false;
-            }
-        }
+        public bool ShowReadOnly { get; set; }
 
         #endregion Public Properties
 
@@ -307,9 +297,6 @@ private void Initialize()
         //
         //---------------------------------------------------
         //#region Private Fields
-
-        private bool _showReadOnly = false;
-
         //#endregion Private Fields        
     }
 }