how to export datagridview data to pipe separated text in c#

I want to export data datagridview to excel for using this code:-

 Microsoft.Office.Interop.Excel._Application app = new Microsoft.Office.Interop.Excel.Application();




                // creating new WorkBook within Excel application
                Microsoft.Office.Interop.Excel._Workbook workbook = app.Workbooks.Add(Type.Missing);




                // creating new Excelsheet in workbook
                Microsoft.Office.Interop.Excel._Worksheet worksheet = null;


                // see the excel sheet behind the program
                app.Visible = true;


                // get the reference of first sheet. By default its name is Sheet1.
                // store its reference to worksheet
                worksheet = (Microsoft.Office.Interop.Excel.Worksheet)workbook.Sheets["Sheet1"];
                worksheet = (Microsoft.Office.Interop.Excel.Worksheet)workbook.ActiveSheet;


                // changing the name of active sheet
                worksheet.Name = "UUSProducts";




                // storing header part in Excel
                for (int i = 1; i < dataGridView1.Columns.Count + 1; i++)
                {
                    worksheet.Cells[1, i] = dataGridView1.Columns[i - 1].HeaderText;
                }






                // storing Each row and column value to excel sheet
                for (int i = 0; i < dataGridView1.Rows.Count - 1; i++)
                {
                    for (int j = 0; j < dataGridView1.Columns.Count; j++)
                    {
                        worksheet.Cells[i + 2, j + 1] = dataGridView1.Rows[i].Cells[j].Value.ToString();
                    }
                }




                // save the application
                workbook.SaveAs("c:\\UUSProducts.xls", Type.Missing, Type.Missing, Type.Missing, Type.Missing, Type.Missing, Microsoft.Office.Interop.Excel.XlSaveAsAccessMode.xlNoChange, Type.Missing, Type.Missing, Type.Missing, Type.Missing);




                // Exit from the application
                app.Quit();

but this code successfully run but when i importing this excel file so getting exception: "External table is not in the expected format" i am using .xls format for excel.

So, how can we remove this exception?
Please help me.

Ankit Agarwal
Softeware Engineer

Column header added...

Note : The table variable should be your data source of the gridview control. Or you can use gridview.DataSource(with type casting).

 string temp = string.Empty;


            foreach (DataColumn colx in table.Columns)
            {
                temp = temp + colx.ColumnName + "|";
            }
            temp = temp + Environment.NewLine;


            foreach (DataRow item in table.Rows)
            {
                foreach(string str in item.ItemArray)
               {
                   temp = temp + str + "|";
               }
               temp = temp + Environment.NewLine;
            }
            System.IO.File.AppendAllText(@"c:\temp.psv",temp);

Without header....