datagridview导出0开头的数字串后，开头的0没了

winform中的datagridview中的带0开头的字符串，导出后，开头的0不见了。比如:员工编号：00011，导出成EXCEL后，只有11，而不是00011.
有人说在导出的语句加上“‘”，但是这样导出后把’也加进了并显示了，变成了‘00011.
请问有没有更好的办法，代码如下，请指导。

saveFileDialog.Filter = "execl files (*.xls)|*.xls";
saveFileDialog.FilterIndex = 0;
saveFileDialog.RestoreDirectory = true;
saveFileDialog.CreatePrompt = true;
saveFileDialog.Title = "导出文件保存路径";
saveFileDialog.ShowDialog();
progreesBar.Visible = true;
Stream myStream;
myStream = saveFileDialog.OpenFile();
StreamWriter sw = new StreamWriter(myStream, System.Text.Encoding.GetEncoding("gb2312"));
//StreamWriter sw = new StreamWriter(myStream, System.Text.Encoding.GetEncoding(-0));
string str = "";
try
{
//写标题
for (int i = 0; i < gridView.ColumnCount; i++)
{
if (i > 0)
{
str += "\t";
}
str += gridView.Columns[i].HeaderText;
}
sw.WriteLine(str);
//写内容
for (int j = 0; j < gridView.Rows.Count - 1; j++)
{
string tempStr = "";
for (int k = 0; k < gridView.Columns.Count; k++)
{
if (k > 0)
{
tempStr += "\t";
}
tempStr += "' " + gridView.Rows[j].Cells[k].Value.ToString(); }
sw.WriteLine(tempStr);
progreesBar.Value += 100 / gridView.RowCount;
}
sw.Close();
myStream.Close();
progreesBar.Value = 100;
MessageBox.Show("数据已经成功导出到：" + saveFileDialog.FileName.ToString(), "导出完成", MessageBoxButtons.OK, MessageBoxIcon.Information);
progreesBar.Value = 0;
progreesBar.Visible = false;