Wait message in Sharepoint

For Client Side  code


//////////////////Wait and Close Dialog box//////////

    function WaitMessage() {
        window.parent.eval("window.waitDialog = SP.UI.ModalDialog.showWaitScreenWithNoClose('Wait request is processing..', '', 90, 50);");
    }

// close message
    function CloseWaitDialog() {
        if (window.frameElement != null) {
            if (window.parent.waitDialog != null) {
                window.parent.waitDialog.close();
            }
        }
        else
        {
            if (window.parent.waitDialog != null)
            {
                window.parent.waitDialog.close();
            }
        }

    }
//////////////////////////////


Use like below

<script>
$(document).ready(function () {
    SP.SOD.executeFunc('sp.js', 'SP.ClientContext', readyFunction);
});

function readyFunction() {
    WaitMessage();
 
////////////////////Write your long code here
 
    CloseWaitDialog();
}
</script>



if you want to call it server side please put the code like below


<asp:Button runat="server" ID="Button" Text="Submit" OnClick="Button_Click" OnClientClick="javascript:WaitMessage();" />

protected void Button_Click(object sender, EventArgs e)
         {
              // Do the complex operations here and at the end of the complex operation, we need to close the dialog box which we opened.

             this.ClientScript.RegisterStartupScript(this.GetType(), "CloseWaitDialog", @"
                     <script language='javascript'>
                         if (window.frameElement != null) {
                             if (window.parent.waitDialog != null) {
                                 window.parent.waitDialog.close();
                             }
                         }
                     </script>");
         }