[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;  
         }  
     }