New Post: Problem to response the xls File to the Client

First off, I just wanted to point out that your issue is not with NPOI.

Next, looking at your code, I believe you may need to add the content size to the response header.

Try adding the following immediately after the addition of the Content-Disposition to the header:

Context.Response.AddHeader("Content-Length", exportData.Length.ToString());

If that doesn't solve your problem, try changing the Content-Type from application/vnd.ms-excel to application/octet-stream.

-MindCore