How to save an Excel Spreadsheet (XLS) to a Database (.DBF) file

private string _fileLocation;

        public SpreadsheetApplication()
        {
            InitializeComponent();
        }

        private void btnOpenFile_Click(object sender, EventArgs e)
        {
            //Opens the openfiledialog box so the user can navigate to the spreadsheet. 
            if (openfiledialog.ShowDialog() == DialogResult.OK)
            {
                //Sets the .text property of the text box to be the file selected in the openfiledialog
                txtBxFileLocation.Text = openfiledialog.FileName;
                //Sets the _fileLocation to be the textbox.text value
                _fileLocation = txtBxFileLocation.Text;
            }
        }

        private void btnProcess_Click(object sender, EventArgs e)
        {
            try
            {
                if (txtBxNameFile.TextLength <= 0)
                {
                    MessageBox.Show("Please can you enter a name for the new CSV file.", "Please enter a name", MessageBoxButtons.OK, MessageBoxIcon.Warning);
                }
                else
                {
                    //Calls the ConvertExcelToCsv method and sets the arguments (Worksheet argument value is hard coded below)
                    ConvertExcelToCsv(_fileLocation, txtBxNameFile.Text + ".csv");
                }
            }
            catch
            {
                MessageBox.Show("You need to select your spreadsheet.", "Select Spreadsheet", MessageBoxButtons.OK, MessageBoxIcon.Error);
            }
        }

        static void ConvertExcelToCsv(string excelFilePath, string csvOutputFile, int worksheetNumber = 1)
        {
            //Checks if the two files required exist or not and then throws an exception. 
            if (!File.Exists(excelFilePath)) throw new FileNotFoundException(excelFilePath);
            if (File.Exists(csvOutputFile)) throw new ArgumentException("File exists: " + csvOutputFile);

            // connection string for XLS
            var cnnStr = String.Format("Provider=Microsoft.Jet.OLEDB.4.0;Data Source={0};Extended Properties=\"Excel 8.0;IMEX=1;HDR=NO\"", excelFilePath);

            ///Connection String for XLSX
            //var cnnStr = String.Format("Provider=Microsoft.ACE.OLEDB.12.0;Data Source={0};Extended Properties=\"Excel 12.0;IMEX=1;HDR=YES\"", excelFilePath);

            //Creates a new OleDbConnection with an argument of cnnStr
            var cnn = new OleDbConnection(cnnStr);

            //creates new datatable in memory to store the read excel spreadsheet.
            var dt = new DataTable();

            try
            {
                //Opens the new connection called "cnn". 
                cnn.Open();
                var schemaTable = cnn.GetOleDbSchemaTable(OleDbSchemaGuid.Tables, null);
                if (schemaTable.Rows.Count < worksheetNumber) throw new ArgumentException("The worksheet number provided cannot be found in the spreadsheet");
                string worksheet = schemaTable.Rows[worksheetNumber - 1]["table_name"].ToString().Replace("'", "");
                string sql = String.Format("select * from [{0}]", worksheet);
                var da = new OleDbDataAdapter(sql, cnn);
                da.Fill(dt);
            }
            catch (Exception e)
            {
                throw e;
            }
            finally
            {
                // close resources
                cnn.Close();
            }

            // write out CSV data
            using (var wtr = new StreamWriter(csvOutputFile))
            {
                foreach (DataRow row in dt.Rows)
                {
                    bool firstLine = true;
                    foreach (DataColumn col in dt.Columns)
                    {
                        if (!firstLine) { wtr.Write(","); } else { firstLine = false; }
                        var data = row[col.ColumnName].ToString().Replace("\"", "\"\"");
                        wtr.Write("\"{0}\"", data);
                    }
                    wtr.WriteLine();

                }
                MessageBox.Show("Spreadsheet has finished processing.", "Information", MessageBoxButtons.OK, MessageBoxIcon.Information);
            }
        }
    }
}