Datagridview exception : System Exception : SomeText in Grid... is not a valid value for double

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C#

Datagridview exception : System Exception : SomeText in Grid... is not a valid value for double . input string is not in a correct format

i use to import the excel file to datagridview and hide it in my program.

the marge cell in excel only show in first cell in datagridview. like if there was a

merge cell in cell 1 and 2 the string will just only appear in cell 1

so i design to loop and add that string in the second cell and keep doing this with all

the merge cell. i got the error with just! only one column it was like it is except only

integer and double value any one have any clue ? Here is my code

PS: Sorry if my English is bad : (

private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
{
    try
    {
        dataGridView3.DataSource = null;
        string FileName = openFileDialog4.FileName; 
path.GetFileName
        if (FileName == "openFileDialog4" || FileName == null)
        {
            FileName = dragtamp;
        }
        OleDbConnection con = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=" + FileName + @";Extended Properties=""Excel 8.0;IMEX=1;HDR=NO;TypeGuessRows=0;ImportMixedTypes=Text""");
        con.Open();
        DataTable dts = new DataTable();
        dts = con.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
        if (dts == null)
        {
            //return null;
        }
        String[] excelSheets = new String[dts.Rows.Count];
        int ii = 0;
        foreach (DataRow row in dts.Rows)
        {
            excelSheets[ii] = row["TABLE_NAME"].ToString();
            ii++;
        }
        List<string> SheeTemp = new List<string>();
        SheeTemp.Clear();
        string[] sheetTemp = new string[5];
        for (int j = 0; j < excelSheets.Length; j++)
        {
            SheeTemp.Add(excelSheets[j]);
            // Query each excel sheet.
        }
        for (int l = 0; l < SheeTemp.Count; l++)
        {
            sheetTemp = SheeTemp[l].Split('$');
            if (sheetTemp[1] == "" || sheetTemp[1] == " ")
            {

            }
            else
            {
                SheeTemp.RemoveAt(l);
            }
        }

        string X = comboBox1.GetItemText(comboBox1.SelectedItem);
        string strSQL = "SELECT * FROM [" + X + "]";
        //string strSQL = "SELECT * FROM [T7AA（130725）$]";
        OleDbCommand com;
        com = new OleDbCommand(strSQL, con);
        OleDbDataReader odr;
        com.Parameters.Clear();
        odr = com.ExecuteReader();
        DataTable dt = new DataTable();
        ChangeIntJpnToIntEngTable(dt);
        if (odr.HasRows)
        {
            dt.Load(odr);
            //dataGridView1.Columns[3].Visible = false;
            //dataGridView1.Columns[2].Visible = false;
            //dataGridView1.Columns[1].Visible = false;
            //dataGridView1.Columns[0].Visible = false;

            dataGridView3.DataSource = dt;
            //dataGridView2.Rows.RemoveAt(0);
            List<int> deleteunwanteddata = new List<int>();
            int tempCounterfordelete = 0;
            for (int i = 0; i < dataGridView3.Rows.Count; i++)
            {
                tempCounterfordelete++;
                if (Convert.ToString(dataGridView3.Rows[i].Cells[1].Value) == "機種\nｺｰﾄﾞ")
                {
                    i = dataGridView3.Rows.Count;
                }
                deleteunwanteddata.Add(tempCounterfordelete);

            }
            for (int i = 0; i <= deleteunwanteddata.Count - 2; i++)
            {
                dataGridView3.Rows.RemoveAt(0);
            }
            DataTable newdt = new DataTable();
            dataGridView4.Rows.Clear();
            dataGridView4.Columns.Clear();

            for (int i = 0; i < dataGridView3.Columns.Count; i++)
            {
                dataGridView4.Columns.Add(Convert.ToString(i),Convert.ToString(i));
                dataGridView4.Rows.Add();
                for (int iam = 0; iam < dataGridView3.Rows.Count; iam++)
                {
                    dataGridView4.Rows.Add();
                }
            }
            string TEMPGRID3 = "" ;

            for (int i = 0; i < dataGridView3.Rows.Count; i++)
            {
                for (int lll = 0; lll < dataGridView3.Columns.Count; lll++)
                { 
                    TEMPGRID3 = Convert.ToString(dataGridView3.Rows[i].Cells[lll].Value);
                     dataGridView4.Rows[i].Cells[lll].Value = TEMPGRID3;
                }
            }
            for (int i = 0; i < dataGridView3.Columns.Count - 1; i++)
            {

                if (Convert.ToString(dataGridView3.Rows[0].Cells[i].Value) == null || Convert.ToString(dataGridView3.Rows[0].Cells[i].Value) == "")
                {
// here is the line that i add a string to the other merge cell and the exception was //appear after this line below was excecuted
                    if (i > 0)
                    {
                        dataGridView3.Rows[0].Cells[i].Value = Convert.ToString(dataGridView3.Rows[0].Cells[i - 1].Value);
                    }
                }
            }
            //------------------------------------------------------------------------------------ใส่ HEADER ให้เหมือนกันแล้ววววววววววว
            for (int i = 7; i < dataGridView3.Rows.Count - 1; i++)
            {
                string chk;
                chk = Convert.ToString(dataGridView3.Rows[i].Cells[1].Value);
                if (chk == "0" || chk == "1" || chk == "2" || chk == "3" || chk == "4" || chk == "5" || chk == "6" || chk == "7" || chk == "8" || chk == "9")
                {
                    dataGridView3.Rows[i].Cells[1].Value = "0" + chk;
                }
            }
            for (int i = 7; i < dataGridView3.Rows.Count - 1; i++)
            {
                string chk;
                chk = Convert.ToString(dataGridView3.Rows[i].Cells[2].Value);
                if (chk == "0" || chk == "1" || chk == "2" || chk == "3" || chk == "4" || chk == "5" || chk == "6" || chk == "7" || chk == "8" || chk == "9")
                {
                    dataGridView3.Rows[i].Cells[2].Value = "0" + chk;
                }
            }
            bool splitstatus = false;
            int SplitCounter = 0;
            int temppointer;
            for (int i = 0; i < dataGridView3.Rows.Count; i++)
            {
                splitstatus = false;
                for (int k = 0; k < dataGridView3.Columns.Count; k++)
                {
                    Counter++;
                    if (Convert.ToString(dataGridView3.Rows[i].Cells[k].Value) == "" || Convert.ToString(dataGridView3.Rows[i].Cells[k].Value) == " " || Convert.ToString(dataGridView3.Rows[i].Cells[k].Value) == null)
                    {
                        splitstatus = true;
                    }
                    if (splitstatus == false)
                    {
                        temppointer = i;
                    }
                }
            }
        }