C#导出Excel动态列

string _sPath = GenerateSalaryMonthlyReport(dgvSalarySum);
System.Diagnostics.Process.Start(_sPath);

public String GenerateSalaryMonthlyReport(DataGridView dgvData)
{
String _sPath = String.Format(@".\{0}.txt", BaseClass.getGUID());
String _sGoal = String.Format(@"{0}{1}.xls", System.Configuration.ConfigurationManager.AppSettings["Statistic"],
BaseClass.ExcelFileName("员工每月薪酬表"));

System.IO.StreamWriter _sw = new System.IO.StreamWriter(_sPath, false, Encoding.Default);

//表头
_sw.WriteLine("人力宝人力资源管理系统V2.0");
_sw.WriteLine("薪酬管理模块 <<员工每月薪酬表>>");
_sw.WriteLine();

_sw.Write(String.Format("{0}\t", "序号"));
foreach (DataGridViewColumn dgvc in dgvData.Columns)
{
if (dgvc.Visible)
{
_sw.Write(String.Format("{0}\t", dgvc.HeaderText));
}
}
_sw.Write(String.Format("{0}\t{1}\t{2}", "员工签字", "日期", "备注"));
_sw.WriteLine();

int i = 1;
foreach (DataGridViewRow dgvr in dgvData.Rows)
{
_sw.Write(String.Format("{0}", i));
for (int j = 0; j < dgvData.Columns.Count - 1; j++)
{
if (dgvData.Columns[j].Visible)
{
if (j == 3)
{
_sw.Write(String.Format("\t'{0}", dgvr.Cells[j].Value));
}
else
{
_sw.Write(String.Format("\t{0}", dgvr.Cells[j].Value));
}
}
}

i++;
_sw.WriteLine();
}
_sw.WriteLine();
_sw.WriteLine(String.Format("{0}\t\t{1}\t\t\t\t{2}\t\t{3}", "制表人", "制表日期", "审核人", "审核日期"));
_sw.Close();
System.IO.File.Move(_sPath, _sGoal);
return _sGoal;
}