将DataTable数据导出到Excell中文为乱码,怎样设置?

public void CreateExcell(String FileName)
{
                    dt = Companyinfo.GetList("");   //DataTable获取
                    System.Web.UI.WebControls.DataGrid dataGrid = new System.Web.UI.WebControls.DataGrid();
                    dataGrid.DataSource = dt.DefaultView;
                    dataGrid.AllowPaging = false;
                    dataGrid.HeaderStyle.BackColor = System.Drawing.Color.Green;
                    dataGrid.HeaderStyle.Font.Bold = true;
                    dataGrid.DataBind();
           
                    System.IO.StringWriter tw = new System.IO.StringWriter();
                    System.Web.UI.HtmlTextWriter hw = new System.Web.UI.HtmlTextWriter(tw);
                    dataGrid.RenderControl(hw);                    string filePath = ConfigurationManager.AppSettings["SaveExcellFile"].ToString() + FileName;
                    System.IO.StreamWriter sw = System.IO.File.CreateText(filePath);
                    sw.Write(tw.ToString());   //创建可写入
                       sw.Close();}//PS :  不能在此函中使用  页面Page对象,即   page.Response;