UpDownBase: found issue in .NET 3.5 version with updating text.

ExtendedWPFToolkitSolution/Src/WPFToolkit.Extended/Core/Primitives/UpDownBase.cs

@@ -74,7 +74,7 @@ namespace Microsoft.Windows.Controls.Primitives
         }
 
         protected virtual T OnCoerceValue(T value)
-        {            
+        {
             return value;
         }
 
@@ -92,7 +92,7 @@ namespace Microsoft.Windows.Controls.Primitives
             RoutedPropertyChangedEventArgs<T> args = new RoutedPropertyChangedEventArgs<T>(oldValue, newValue);
             args.RoutedEvent = ValueChangedEvent;
             RaiseEvent(args);
-        }        
+        }
 
         #endregion //Value
 
@@ -259,7 +259,8 @@ namespace Microsoft.Windows.Controls.Primitives
 
 #if VS2008
             //there is a bug in .NET 3.5 which will not correctly update the textbox text through binding.
-            TextBox.Text = Text;
+            if (TextBox != null)
+                TextBox.Text = Text;
 #endif
 
             _isSyncingTextAndValueProperties = false;