Silverlight water mark textbox?

I am developing a sample text box in Silverlight 4. I want 开发者_如何学Cto have a watermark in the textbox. I used tags but it didn't work. Please can any one help how to add a watermark to text boxes in Silver light 4.0.

You may find samples (or idea of how to implement it yourself) in the following links:

• http://joyfulwpf.blogspot.com/2009/02/creating-wpf-watermarked-textbox-using.html
• http://timheuer.com/blog/archive/2008/10/22/silverlight-watermark-text-box-control.aspx