通过IO流写入Excel

从网络上看到excel一条一条的插入数据很慢，有人通过流写入excel，速度很快，具体原理如下：

    1.使用的是StreamWriter sw = new StreamWriter(path, false,Encoding.GetEncoding("gb2312"));最终生成文件
    2.使用  StringBuilder sb = new StringBuilder();类把查询出来的数据组合为一句超长字符串一次性插入到excel中，
    sb.Append(ds.Tables[0].Columns[k].ColumnName.ToString() + "\t");
    注意，可不能漏了"\t" 这个是非常重要的！ 因为c# "\t"就等于 键盘上的Tab [朋友们可以试试：打开新的txt然后输入1按Tab，输入2按Tab，输入3按Tab保存，然后打开excel文件  把刚刚保存的txt文件拉进去打开你就发现原来。这样写的话1 2 3 会分别在每个单元格上的了。所以上面才使用 "\t"连起来数据库出来的那堆数据，这样一次性导进去，他们就会按照每个单元格来填充！
    需要引用：
    using System.Threading;
    using System.IO;
    方法如下：
     private void button1_Click(object sender, EventArgs e)
            {           
                saveFileDialog1.Title = "保存的excel文件";
                saveFileDialog1.InitialDirectory = "c:\\";
                saveFileDialog1.Filter = "Excel97-2003 (*.xls)|*.xls|Excel07-2010(*.xlsx)|*.xlsx;
                saveFileDialog1.ShowDialog();
                if (saveFileDialog1.FileName == "" || saveFileDialog1.FileName == null)
                {
                    MessageBox.Show("文件名不能为空!");
                    return;
                }
                string path = saveFileDialog1.FileName;
                string constr = "Data Source=.;Initial Catalog=Exhibition;User ID=sa;Password=";
                string sql = GetStrSql();
                DataSet ds=new DataSet();
                using (SqlConnection con = new SqlConnection(constr))
                {
                    SqlDataAdapter da = new SqlDataAdapter(sql, con);
                    da.Fill(ds);
                }
                if (ds == null)
                {
                    MessageBox.Show("数据获取有误!");
                    return;
                }
                WriteExcel(ds, path);     
            }
     
     public void WriteExcel(DataSet ds, string path)
            {
                try
                {
                    long totalCount = ds.Tables[0].Rows.Count;
                    lblTip.Text = "共有" + totalCount + "条数据。";
                    Thread.Sleep(1000);
                    long rowRead = 0;
                    float percent = 0;
     
                    StreamWriter sw = new StreamWriter(path, false,Encoding.GetEncoding("gb2312"));
                    StringBuilder sb = new StringBuilder();
                    for (int k = 0; k < ds.Tables[0].Columns.Count; k++)
                    {
                        sb.Append(ds.Tables[0].Columns[k].ColumnName.ToString() + "\t");
                    }
                    sb.Append(Environment.NewLine);
     
                    for (int i = 0; i < ds.Tables[0].Rows.Count; i++)
                    {
                        rowRead++;
                        percent = ((float)(100 * rowRead)) / totalCount;
                        Pbar.Maximum = (int)totalCount;
                        Pbar.Value = (int)rowRead;
                        lblTip.Text = "正在写入[" + percent.ToString("0.00") + "%]...的数据";
                        System.Windows.Forms.Application.DoEvents();
     
                        for (int j = 0; j < ds.Tables[0].Columns.Count; j++)
                        {
                            sb.Append(ds.Tables[0].Rows[i][j].ToString() + "\t");
                        }
                        sb.Append(Environment.NewLine);
                    }
                    sw.Write(sb.ToString());
                    sw.Flush();
                    sw.Close();
                    MessageBox.Show("已经生成指定Excel文件!");
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }           
            }
     
    public string GetStrSql()
            {
                string strSql = "select a from b";
                return strSql;
            }