Issue of validation control

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ASP.NET

I have 2 validaion control which is used to validate mobile number below is source code

<asp:TextBox ID="txtMobileNumber1" runat="server" Width="200px"></asp:TextBox>

<asp:RegularExpressionValidator ID="revMobileNumber1" runat="server"
ControlToValidate="txtMobileNumber1" ErrorMessage="Please Enter Number Only"ForeColor="Red" ValidationExpression="^\d+$"></asp:RegularExpressionValidator>

<asp:RegularExpressionValidator ID="RegularExpressionValidator1"  runat="server"ValidationExpression="((\(\d{3}\) ?)|(\d{3}-))?\d{3}-\d{4}" ErrorMessage="Mobile Number should be 10 Digit" ControlToValidate="txtMobileNumber1"></asp:RegularExpressionValidator>

I want if user enter charcater than it display first error "please enter number" and second error should not display "Mobile Number should be 10 digit".but in my case it display both error message.i want only one message at time. i have only one button control.