导入excel到datagridview输出追加

using System;
using System.Data;
using System.Windows.Forms;
using Excel = Microsoft.Office.Interop.Excel;

namespace ExcelImportApp
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
        }

        private void btnImport_Click(object sender, EventArgs e)
        {
            OpenFileDialog openFileDialog = new OpenFileDialog();
            openFileDialog.Filter = "Excel Files|*.xls;*.xlsx;*.xlsm";
            if (openFileDialog.ShowDialog() == DialogResult.OK)
            {
                string filePath = openFileDialog.FileName;
                Excel.Application excelApp = new Excel.Application();
                Excel.Workbook workbook = excelApp.Workbooks.Open(filePath);
                Excel.Worksheet worksheet = workbook.Sheets[1];
                Excel.Range range = worksheet.UsedRange;

                for (int row = 1; row <= range.Rows.Count; row++)
                {
                    DataGridViewRow dataGridViewRow = new DataGridViewRow();
                    dataGridViewRow.CreateCells(dataGridView);
                    for (int col = 1; col <= range.Columns.Count; col++)
                    {
                        dataGridViewRow.Cells[col - 1].Value = range.Cells[row, col].Value;
                    }
                    dataGridView.Rows.Add(dataGridViewRow);
                }

                workbook.Close();
                excelApp.Quit();
            }
        }
    }
}