Import data not save in database

using window application to import csv data to sql server.here the code i tried. Not get any error but the import data cannot save  in database.

code: 

private void btnselect_Click(object sender, EventArgs e)
{
    //open serach file to recognise by the 
    OpenFileDialog ofd = new OpenFileDialog();
    ofd.DefaultExt = ".csv";
    ofd.Filter = "Comma Separated(*.csv)|*.csv";
    ofd.ShowDialog();
    textfilename.Text = ofd.FileName;

}

private DataTable GetDataTabletFromCSVFile(string csv_file_path)
{
    DataTable csvData = new DataTable();
    try
    {
        using (TextFieldParser csvReader = new TextFieldParser(csv_file_path))
        {
            csvReader.SetDelimiters(new string[] { "," });
            csvReader.HasFieldsEnclosedInQuotes = true;
            string[] colfields = csvReader.ReadFields();
            foreach(string column in colfields)
            {
                while (! csvReader.EndOfData)
                {
                    string[] fieldData = csvReader.ReadFields();
                    
                    for (int i = 0; i < fieldData.Length; i++)
                    {
                        if (fieldData[i] == "")
                        {
                            fieldData[i] = null;
                        }
                    }
                    csvData.Rows.Add(fieldData);
                }
            }
        }
    }
    catch (Exception ex)
    {
        return null;
    }
    return csvData;

}
private void btnImport_Click(object sender, EventArgs e)
{
    {
        Cursor = Cursors.WaitCursor;
        DataTable dt = GetDataTabletFromCSVFile(csv_file_path);
        if (dt == null) return;
        SaveImportDataToDatabase(dt);
        MessageBox.Show("Data Import success!");
        textfilename.Text = string.Empty;
        Cursor = Cursors.Default;
    }
}

private void SaveImportDataToDatabase(DataTable SS)
{
using (SqlConnection conn =  new SqlConnection())    
using (SqlConnection dbConnection = new SqlConnection("Data Source=ytl//bku; Initial Catalog=databse; User Id=***; Password=*****;"))
    {
        dbConnection.Open();
        using (SqlBulkCopy s = new SqlBulkCopy(dbConnection))
        {
            s.DestinationTableName = "SS";
            foreach (var column in SS.Columns)
                s.ColumnMappings.Add(column.ToString(), column.ToString());

            s.WriteToServer(SS);
            
        }
    }
}