How to disable postback on an asp Button (System.Web.UI.WebControls.Button)

Question

Have your javascript return false when it's done.

<asp:button runat="server".... OnClientClick="myfunction(); return false;" />

YourButton.Attributes.Add("onclick", "return false");

or

<asp:button runat="server" ... OnClientClick="return false" />

You can use jquery click action and use the preventDefault() function to avoid postback

<asp:button ID="btnMyButton" runat="server" Text="MyButton" />


$("#btnMyButton").click(function (e) {
// some actions here
 e.preventDefault();
}

Consider this.

<script type="text/javascript">
Sys.WebForms.PageRequestManager.getInstance().add_beginRequest(BeginRequest);
function BeginRequest(sender, e) {
    e.get_postBackElement().disabled = true;

}
     </script>

The others are right that you need your callback to return false; however I'd like to add that doing it by setting the onclick is an ugly old way of doing things. I'd recommend reading about unobtrusive javascript. Using a library like jQuery could make your life easier, and the HTML less coupled to your javascript (and jQuery's supported by Microsoft now!)