Ever have the need for a user to enter a date into a textbox, but not sure how to validate that they actually did?
<asp:CompareValidator id="dateValidator" runat="server" Type="Date" Operator="DataTypeCheck" ControlToValidate="dateTextbox" ErrorMessage="Please enter a valid date."> </asp:CompareValidator>
This beats the heck out of writing my own code to do this, and surely this is better tested as well. ;)