Usually, in Grid export, waitingpopup cannot be rendered. Due to the full post, we cannot handle the Waitingpopup. However, this KB overcome those behavior using Browser Cookies.
Initialize the Grid:
In the ToolbarClick event, show the popup and set an interval to watch for the cookies from the server response. Once the cookies were found, clear the interval and hide the popup.
Before returning the response/exported file to the client-end, set the Cookies.
Figure: Grid Exporting with Popup
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