Save Headers from datagridview to excel? save as Excel 2007 format (.xlsx)?

Question

I am trying to create a program whereby i import data from an excel file(.xlsx), make changes to it and then save it back to the excel file. I have a couple of issues im stuck with which i hope you could help me with :

1. When i export the datagridview back to Excel, it misses out the headers, how can i get it to export these as well? Everything else exports fine.

2. At the moment it seems i can only save the export as a .xls file, how can i save it as a .xlsx file. I have changed the filename to xlsx, it creates the file but i cant view it in excel because the format is incorrect.

3. Finally as above i wanted to save it to the original Excel file where i imported to the datagridview, however i get an error saying the "cannot access ...../debug folder, it may be corrupt or read only".

The following is the code for importing the the Excel (.xlsx) data to the datagridview

public Form1()
    {
        InitializeComponent();

        // populate the dataGridView with the Excel File
        string connectionString = String.Format(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0}; Extended Properties=""Excel 8.0;HDR=YES;IMEX=1;
                                               """, @"C:\Documents and Settings\User\Desktop\Visual Studio\GBstock\GBstock\bin\Debug\FORM TEST.xlsx");
        string query = String.Format("select * from [{0}$]", "Sheet1");
        OleDbDataAdapter dataAdapter = new OleDbDataAdapter(query, connectionString);
        DataSet dataSet = new DataSet();
        dataAdapter.Fill(dataSet);
        dataGridView1.DataSource = dataSet.Tables[0];

        // populates the comboBox (cbSuppList) with all column headers
        for (int i = 3; i < dataGridView1.Columns.Count; i++)
            {
                cbSuppList.Items.Add(dataGridView1.Columns[i].HeaderText);
            }
    }

The following is the "Save" code from datagridview to Excel, allbeit .xls format

private void btnSave_Click(object sender, EventArgs e)
    {
        Excel.Application xlApp;
        Excel.Workbook xlWorkBook;
        Excel.Worksheet xlWorkSheet;
        object misValue = System.Reflection.Missing.Value;

        xlApp = new Excel.Application();
        xlWorkBook = xlApp.Workbooks.Add(misValue);
        xlWorkSheet = (Excel.Worksheet)xlWorkBook.Worksheets.get_Item(1);
        int i = 0;
        int j = 0;

        for (i = 0; i <= dataGridView1.Rows.Count - 1; i++)
        {
            for (j = 0; j <= dataGridView1.Columns.Count - 1; j++)
            {
                DataGridViewCell cell = dataGridView1[j, i];
                xlWorkSheet.Cells[i + 1, j + 1] = cell.Value;
            }
        }
        xlWorkBook.SaveAs("C:/Documents and Settings/User/Desktop/Visual Studio/GBstock/GBstock/bin/Debug/FORM TEST.xls", Excel.XlFileFormat.xlWorkbookNormal, misValue, misValue, misValue, misValue, Excel.XlSaveAsAccessMode.xlExclusive, misValue, misValue, misValue, misValue, misValue);
        xlWorkBook.Close(true, misValue, misValue);
        xlApp.Quit();
    }

Answer 1

1. You never use the HeaderText, like:
   dataGridView1.Columns[X].HeaderText Before your first for loop, you may loop the column (as your second for loop) using the previous line (with X the column's index). The basic idea:

   for (int index = 0; index <= dataGridView1.Columns.Count - 1; index ++)
   {
   //dataGridView1.Columns[index ].HeaderText
   }

2. Before Office 2007, you can use your method.
   But, with Office 2007 and more, you have to use OpenXML
   You can see an example : http://msdn.microsoft.com/en-us/library/bb508943(v=office.12).aspx You also may find some ressources in code project .

3. Have you disposed all ressources used?
   Also, if you write xls data to xslx file, it's not the correct format (as you see)... If your dataAdapter is not disposed , the file may be lock (you cannot overwrite it). But, it may be an other error (where do you have the exception? what is the exception's type?)