textbox 只能输入数字 不为空

<asp:TextBox ID="txtPageNum" runat="server" CssClass="txtInput2 small2" AutoPostBack="True"
                OnTextChanged="txtPageNum_TextChanged" onkeypress="return (/[\d]/.test(String.fromCharCode(event.keyCode)));" >10</asp:TextBox>
            <asp:RegularExpressionValidator ID="revEnterNum" runat="server" ControlToValidate="txtPageNum"
                Display="Dynamic" ErrorMessage="请输入数字！" ValidationExpression="^([1-9][0-9]*)$"></asp:RegularExpressionValidator>
            <asp:RequiredFieldValidator ID="rfvNotEmpty" runat="server" ControlToValidate="txtPageNum"
                Display="Dynamic" ErrorMessage="不能为空，请输入数字！"></asp:RequiredFieldValidator>

 ////设置分页数量
    protected void txtPageNum_TextChanged(object sender, EventArgs e)
    {
        Page.Validate();
        if (Page.IsValid)
        {
          AspNetPager1.CurrentPageIndex = 1;
          AspNetPager1.PageSize = Convert.ToInt32(txtPageNum.Text.Trim());
          RptBind();
        }
    }