在窗体上加一按钮，单击后，在D盘目录下的123.xls单元格A1里填充文字。

你需要引用excel包，其他的网上有资料，具体我也没操作过，学习

SaveFileDialog saveFileDialog = new SaveFileDialog();
            saveFileDialog.Filter = "Execl files (*.xls)|*.xls";
            saveFileDialog.FilterIndex = 0;
            saveFileDialog.RestoreDirectory = true;
            saveFileDialog.CreatePrompt = true;
            saveFileDialog.Title = "Export Excel File To";

            if (saveFileDialog.ShowDialog() == DialogResult.Cancel)
            {
                return;
            }
            Stream myStream;
            myStream = saveFileDialog.OpenFile();

            int ColumnCount = 3;

            StreamWriter sw = new StreamWriter(myStream, System.Text.Encoding.Unicode);
            string str = "";
            try
            {
                for (int i = 0; i < ColumnCount; i++)   //写标题-------------------------------
                {
                    if (i > 0)
                    {
                        str += "\t";
                    }
                    str += dataGridView2.Columns[i].HeaderText;
                }
                sw.WriteLine(str);

                for (int j = 0; j < dataGridView2.Rows.Count; j++)    //写内容--------------------------------
                {
                    string tempStr = "";
                    for (int k = 0; k < ColumnCount; k++)
                    {
                        if (k > 0)
                        {
                            tempStr += "\t";
                            if (k == 1)
                            {
                                tempStr += "'";
                            }
                        }
                        tempStr += dataGridView2.Rows[j].Cells[k].Value.ToString();
                    }
                    sw.WriteLine(tempStr);
                }
                sw.Close();
                myStream.Close();
                // MessageBox.Show("导出成功！","系统提示");
            }