我试过这样的
<asp:RegularExpressionValidator
ID="RegularExpressionValidator1"
runat="Server"
ControlToValidate="txtWebUrl"
class="red"
ValidationExpression="/[-a-zA-Z0-9@:%_\+.~#?&//=]{2,256}\.[a-z]{2,4}\b(\/[-a-zA-Z0-9@:%_\+.~#?&//=]*)?/gi"
ErrorMessage="Please enter a valid URL"
Display="Dynamic"
/>