我喜欢填充到dateTable再导出：

SqlDataAdapter da=new SqlDataAdapter("select ID,Content from tb1",conn);
DataSet ds=new DataSet();
da.Fill(ds,"table1");
DataTable dt=ds.Tables["table1"];
StringWriter sw=new StringWriter();
sw.WriteLine(" ID,Content ");
foreach(DataRow dr in dt.Rows)
{
sw.WriteLine(dr["ID"]+","+dr["Content"]);
}
sw.Close();
Response.AddHeader("Content-Disposition", "attachment; filename=test.csv");
Response.ContentType = "application/ms-excel";
Response.ContentEncoding=System.Text.Encoding.GetEncoding("GB2312");
Response.Write(sw);
Response.End();