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

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;
}
}