Minimum and Maximum character validation for TextBox using ASP.Net RegularExpression Validator

    <asp:RangeValidator ID="RangeValidator1" runat="server" Display="static" ControlToValidate="txtcpwd"
                                                                    ErrorMessage="Password must be minimum 6 & max 8 charachters" Type="String" MinimumValue="6"
                                                                    MaximumValue="8" Visible="false">
even if i have miminum 6 charchtaers its still displayin the msg