Javascript
<script language="javascript" type="text/javascript"> function disableButton(sender,group) { Page_ClientValidate(group); if (Page_IsValid) { sender.disabled = "disabled"; __doPostBack(sender.name, ''); } } </script>
HTML
<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="TextBox1" ValidationGroup="i" ErrorMessage="RequiredFieldValidator">*</asp:RequiredFieldValidator> <br /> <asp:Button runat="server" ID="btnSave" Text="Save" OnClick="Save" OnClientClick="disableButton(this,'i')" UseSubmitBehavior="false" ValidationGroup="i" />
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Courtesy : Yasser Zaid