C#,WPF,DataGrid,Excel，导出

private void btnExport_Click(object sender, RoutedEventArgs e)
{
System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
sw.Start();
dg.SelectAllCells();
dg.ClipboardCopyMode = DataGridClipboardCopyMode.IncludeHeader;
ApplicationCommands.Copy.Execute(null, dg);
string result = (string)Clipboard.GetData(DataFormats.Text);
SaveFileDialog sfd = new SaveFileDialog();
string dtNow = DateTime.Now.ToString("yyyyMMddHHmmssffff");
sfd.FileName = dtNow + "导出到Excel";
sfd.Filter = "Excel文件(*.xls)|*.xls|Csc文件(*.csv)|*.csv|所有文件(*.*)|*.*";
if(sfd.ShowDialog()==true)
{
string path = System.IO.Path.GetDirectoryName(sfd.FileName);
dg.UnselectAllCells();
StreamWriter swr = new StreamWriter(sfd.FileName);
swr.WriteLine(result.Replace(',', ' '));
swr.Close();
sw.Stop();
string timeSpan = sw.ElapsedMilliseconds.ToString();
long num = dg.Items.Count;
MessageBox.Show("共有" + num + "条数据!\n" + "导出到" + path + "!\n" + "共耗时" + timeSpan + "毫秒!\n");
}
}