WinForm c# GridView导出Excel

WinForm GridView导出Excel
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;
using System.IO;

namespace gridview导出excel
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

SqlConnection con = new SqlConnection("server=.;database=TestDB;uid=sa;pwd=");
private void btnSelect_Click(object sender, EventArgs e)
{
string Sql = "SELECT UserName,UserAge,UserPhone,UserAddress From tb_userinfo";
con.Open();
SqlDataAdapter da;
da = new SqlDataAdapter(Sql, con);
DataSet ds = new DataSet();
da.Fill(ds, "tb_userinfo");
this.dataGridView1.DataSource = ds.Tables["tb_userinfo"].DefaultView;

con.Close();
}

private void btnOut_Click(object sender, EventArgs e)
{
SaveFileDialog saveFileDialog = new SaveFileDialog();
saveFileDialog.Filter = "Execl   files   (*.xls)|*.xls";
saveFileDialog.FilterIndex = 0;
saveFileDialog.RestoreDirectory = true;
saveFileDialog.CreatePrompt = true;
saveFileDialog.Title = "导出Excel文件到";

DateTime now = DateTime.Now;
saveFileDialog.FileName = now.Year.ToString().PadLeft(2)
+ now.Month.ToString().PadLeft(2, '0')
+ now.Day.ToString().PadLeft(2, '0') + "-"
+ now.Hour.ToString().PadLeft(2, '0')
+ now.Minute.ToString().PadLeft(2, '0')
+ now.Second.ToString().PadLeft(2, '0');

saveFileDialog.ShowDialog();

Stream myStream;
myStream = saveFileDialog.OpenFile();
StreamWriter sw = new StreamWriter(myStream, System.Text.Encoding.GetEncoding("gb2312"));
string str = "";
try
{
//写标题
for (int i = 0; i < dataGridView1.ColumnCount; i++)
{
if (i > 0)
{
str += "\t";
}
str += dataGridView1.Columns[i].HeaderText;
}

sw.WriteLine(str);
//写内容
for (int j = 0; j < dataGridView1.Rows.Count; j++)
{
string tempStr = "";
for (int k = 0; k < dataGridView1.Columns.Count; k++)
{
if (k > 0)
{
tempStr += "\t";
}
tempStr += dataGridView1.Rows[j].Cells[k].Value.ToString();
}
sw.WriteLine(tempStr);
}
sw.Close();
myStream.Close();
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString());
}
finally
{
sw.Close();
myStream.Close();
}
}

}

}