TextBlock about the same as WinForms Label .
By MSDN :
The TextBlock control is the main element for displaying text in Silverlight-based applications.
Provides easy controls for displaying small amounts of text ...
EDIT : I just noticed your tag for Silverlight 3. Label should be built into Silverlight 3, so are you sure you are not using 2?
You might want to consider TextBlock depending on how you use it. Again for MSDN :
The Label control displays a signature, a required field indicator, and a user verification error indicator. It is usually used in conjunction with input controls, such as a text box. If you do not need to display a required field or check indicators, you can use TextBlock instead.
Kelsey
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