At least n Characters required

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Last Name: <ASP:TEXTBOX id=TxtLastName runat="server"></ASP:TEXTBOX><ASP:REGULAREXPRESSIONVALIDATOR id=REVLastName runat="server" controltovalidate="TxtLastName" errormessage="please enter at least 3 charaters"

validationexpression="[0-9a-zA-Z]{3,}"></ASP:REGULAREXPRESSIONVALIDATOR>
� Here we used RegularExpressionValidator to validate that user enter at least 3 characters in the Last name TextBox by add this regular expression [0-9a-zA-Z]{3,}.