validate a text box only enter numeric value in javascript in .NET

<asp:RegularExpressionValidator id="RegularExpressionValidator1"  
                       ControlToValidate="TextBox1"  
                       ValidationExpression="\d+"  
                       Display="Static"  
                       EnableClientScript="true"  
                       ErrorMessage="Please enter numbers only"  
                      runat="server"/>

function fncInputNumericValuesOnly()
    {
        if(!(event.keyCode==45||event.keyCode==46||event.keyCode==48||event.keyCode==49||event.keyCode==50||event.keyCode==51||event.keyCode==52||event.keyCode==53||event.keyCode==54||event.keyCode==55||event.keyCode==56||event.keyCode==57))
        {
            event.returnValue=false;
        }
    }