[what's my wrong? and why my file excel don't create file?]

Question

private void btnExportExcel_Click(object sender, EventArgs e)
     {

         string filePath = GetFileNameToSave();

         if (string.IsNullOrEmpty(filePath))
         {
               return;


         }
        pivotGrid.ExportToXlsx(filePath);
         ActionNotifier.Information("Exported file  Excel.");

         System.Diagnostics.Process.Start(filePath);
     }

     static string GetFileNameToSave()
     {
         string fNameDefault = String.Format("{0}.{1}.xlsx", "Export", DateTime.Now.ToString("yy.MM.dd_hh.mm"));
         using (SaveFileDialog dlgSave = new SaveFileDialog { Title = "Export Excel", Filter = "Excel file |*.xlsx ", FileName = fNameDefault })
         {

             dlgSave.OverwritePrompt = true;
             dlgSave.RestoreDirectory = true;
             if (dlgSave.ShowDialog() != DialogResult.OK || !dlgSave.CheckPathExists)

                 return null;

             dlgSave.AddExtension = true;



             string fileName = dlgSave.FileName.Trim();

             if (!fileName.EndsWith(".xlsx"))
                 fileName += ".xlsx";

             return fileName;
         }
     }