title: How can i change mime type for reportviewer?
body: <p>i render and extend with reportviewer but but these code  extend with old file extension.
  For example i want to create with .xlsx but it create xls. how can i change default mimeType? </p>
  
  <pre><code>protected void ExportExcel_Click(object sender, EventArgs e)
  {
      Warning[] warnings;
      string[] streamids;
      string mimeType;
      string encoding;
      string extension;
      string filename;
  
      byte[] bytes = ReportViewer1.LocalReport.Render(
         "Excel", null, out mimeType, out encoding,
          out extension,
         out streamids, out warnings);
  
      filename = string.Format("{0}.{1}", "ExportToExcel", "xls");
      Response.ClearHeaders();
      Response.Clear();
      Response.AddHeader("Content-Disposition", "attachment;filename=" + filename);
      Response.ContentType = mimeType;
      Response.BinaryWrite(bytes);
      Response.Flush();
      Response.End();
  }
  </code></pre>