datagridview中将数据导入到Excel中

 public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            DataTable dt = new DataTable("cart");
            DataColumn dc1 = new DataColumn("areaid", Type.GetType("System.String"));
            DataColumn dc2 = new DataColumn("house", Type.GetType("System.String"));
            DataColumn dc3 = new DataColumn("seq", Type.GetType("System.String"));
            DataColumn dc4 = new DataColumn("remark", Type.GetType("System.String"));

            dt.Columns.Add(dc1);
            dt.Columns.Add(dc2);
            dt.Columns.Add(dc3);
            dt.Columns.Add(dc4);

            DataRow dr = dt.NewRow();
            dr["areaid"] = "北京";
            dr["house"] = "北京";
            dr["seq"] = "2";
            dr["remark"] = "货付款";
            dt.Rows.Add(dr);

            DataRow dr1 = dt.NewRow();
            dr1["areaid"] = "北京";
            dr1["house"] = "上海";
            dr1["seq"] = "1";
            dr1["remark"] = "货付款";
            dt.Rows.Add(dr1);

            DataRow dr2 = dt.NewRow();
            dr2["areaid"] = "上海";
            dr2["house"] = "上海";
            dr2["seq"] = "1";
            dr2["remark"] = "货付款";
            dt.Rows.Add(dr2);

            DataRow dr3 = dt.NewRow();
            dr3["areaid"] = "上海";
            dr3["house"] = "北京";
            dr3["seq"] = "1";
            dr3["remark"] = "付款";
            dt.Rows.Add(dr3);

            string[] columns = {"城市","名称","顺序","备注"};
            OutputXLSFromDataTable(columns, dt, saveFileDialog1);

       
        }

        /// <summary>
        /// 导出DataTable为XLS，并打开生成的XLS
        /// </summary>
        /// <param name="columns">列名</param>
        /// <param name="dt">表</param>
        /// <param name="saveFileDialog">对话框</param>
        /// <returns></returns>
        public static bool OutputXLSFromDataTable(string[] columns, DataTable dt, SaveFileDialog saveFileDialog)
        {
            DialogResult rs = saveFileDialog.ShowDialog();
            if (rs != DialogResult.OK)
            {
                return false;
            }
            try
            {
                ExcelWriter excel = new ExcelWriter(saveFileDialog.FileName);
                excel.BeginWrite();
                short cols = 0;
                if (columns == null || columns.Length == 0)
                {//若没有传列名，则以dt的列名做为Excel的列名
                    foreach (DataColumn col in dt.Columns)
                    {
                        excel.WriteString(0, cols, col.ColumnName);
                        cols++;
                    }
                }
                else
                {
                    foreach (string column in columns)
                    {
                        excel.WriteString(0, cols, column);
                        cols++;
                    }
                }

                short rows = 1;
                foreach (DataRow dr in dt.Rows)
                {
                    cols = 0;
                    foreach (DataColumn col in dt.Columns)
                    {
                        excel.WriteString(rows, cols, dr[col].ToString());
                        cols++;
                    }
                    rows++;
                }
                excel.EndWrite();
                Process.Start(saveFileDialog.FileName);
                return true;
            }
            catch
            {
                return false;
            }
        }

    }

    /// <summary>
    /// 通过文件结构直接生成xls文件
    /// </summary>
    public class ExcelWriter
    {
        FileStream _wirter;
        public ExcelWriter(string strPath)
        {
            _wirter = new FileStream(strPath, FileMode.OpenOrCreate);
        }
        /// <summary>
        /// 写入short数组
        /// </summary>
        /// <param name="values"></param>
        private void _writeFile(short[] values)
        {
            foreach (short v in values)
            {
                byte[] b = BitConverter.GetBytes(v);
                _wirter.Write(b, 0, b.Length);
            }
        }
        /// <summary>
        /// 写文件头
        /// </summary>
        public void BeginWrite()
        {
            _writeFile(new short[] { 0x809, 8, 0, 0x10, 0, 0 });
        }
        /// <summary>
        /// 写文件尾
        /// </summary>
        public void EndWrite()
        {
            _writeFile(new short[] { 0xa, 0 });
            _wirter.Close();
        }
        /// <summary>
        /// 写一个数字到单元格x,y
        /// </summary>
        /// <param name="x"></param>
        /// <param name="y"></param>
        /// <param name="value"></param>
        public void WriteNumber(short x, short y, double value)
        {
            _writeFile(new short[] { 0x203, 14, x, y, 0 });
            byte[] b = BitConverter.GetBytes(value);
            _wirter.Write(b, 0, b.Length);
        }
        /// <summary>
        /// 写一个字符到单元格x,y
        /// </summary>
        /// <param name="x"></param>
        /// <param name="y"></param>
        /// <param name="value"></param>
        public void WriteString(short x, short y, string value)
        {
            byte[] b = Encoding.Default.GetBytes(value);
            _writeFile(new short[] { 0x204, (short)(b.Length + 8), x, y, 0, (short)b.Length });
            _wirter.Write(b, 0, b.Length);
        }
    }