/// <summary>
/// 直接输出Excel
/// </summary>
/// <param name="dtData"></param>
public static void DataTable2Excel(System.Data.DataTable dtData)
　　　　{
　　System.Web.UI.WebControls.DataGrid dgExport = null;
　　　　　　// 当前对话
　　　　　　System.Web.HttpContext curContext = System.Web.HttpContext.Current;
　　　　　　// IO用于导出并返回excel文件
　　　　　　System.IO.StringWriter strWriter = null;
　　　　　　System.Web.UI.HtmlTextWriter htmlWriter = null;

　　　　　　if (dtData != null)
　　　　　　{
　　　　　　　　// 设置编码和附件格式
　　　　　　　　curContext.Response.ContentType = "application/vnd.ms-excel";
　　　　　　　　curContext.Response.ContentEncoding =System.Text.Encoding.UTF8;
　　　　　　　　curContext.Response.Charset = "";

　　　　　　　　// 导出excel文件
　　　　　　　　strWriter = new System.IO.StringWriter();
　　　　　　　　htmlWriter = new System.Web.UI.HtmlTextWriter(strWriter);

　　　　　　　　// 为了解决dgData中可能进行了分页的情况，需要重新定义一个无分页的DataGrid
　　　　　　　　dgExport = new System.Web.UI.WebControls.DataGrid();
　　　　　　　　dgExport.DataSource = dtData.DefaultView;
　　　　　　　　dgExport.AllowPaging = false;
　　　　　　　　dgExport.DataBind();

　　　　　　　　// 返回客户端
　　　　　　　　dgExport.RenderControl(htmlWriter);　　
　　　　　　　　curContext.Response.Write(strWriter.ToString());
　　　　　　　　curContext.Response.End();
　　　　　　}
　　　　}

/// <summary>
/// dtData是要导出为Excel的DataTable,FileName是要导出的Excel文件名(不加.xls)
/// </summary>
/// <param name="dtData"></param>
/// <param name="FileName"></param>
private void DataTable3Excel(System.Data.DataTable dtData, String FileName)
{
System.Web.UI.WebControls.GridView dgExport = null;
//当前对话
System.Web.HttpContext curContext = System.Web.HttpContext.Current;
//IO用于导出并返回excel文件
System.IO.StringWriter strWriter = null;
System.Web.UI.HtmlTextWriter htmlWriter = null;

if (dtData != null)
{
//设置编码和附件格式
//System.Web.HttpUtility.UrlEncode(FileName, System.Text.Encoding.UTF8)作用是方式中文文件名乱码
curContext.Response.AddHeader("content-disposition", "attachment;filename=" + System.Web.HttpUtility.UrlEncode(FileName, System.Text.Encoding.UTF8) + ".xls");
curContext.Response.ContentType = "application nd.ms-excel";
curContext.Response.ContentEncoding = System.Text.Encoding.UTF8;
curContext.Response.Charset = "GB2312";

//导出Excel文件
strWriter = new System.IO.StringWriter();
htmlWriter = new System.Web.UI.HtmlTextWriter(strWriter);

//为了解决dgData中可能进行了分页的情况,需要重新定义一个无分页的GridView
dgExport = new System.Web.UI.WebControls.GridView();
dgExport.DataSource = dtData.DefaultView;
dgExport.AllowPaging = false;
dgExport.DataBind();

//下载到客户端
dgExport.RenderControl(htmlWriter);
curContext.Response.Write(strWriter.ToString());
curContext.Response.End();
}
}

/// <summary>
/// Datatable to Excel带自定文件名的导出
/// </summary>
/// <param name="dt"></param>
/// <param name="FileName"></param>
private void DataTable4Excel(System.Data.DataTable dt, string FileName)
{
System.IO.StringWriter stringWriter = new System.IO.StringWriter();
HtmlTextWriter htmlWriter = new HtmlTextWriter(stringWriter);
DataGrid excel = new DataGrid();
//System.Web.UI.WebControls.TableItemStyle AlternatingStyle = new TableItemStyle();
System.Web.UI.WebControls.TableItemStyle headerStyle = new TableItemStyle();
//System.Web.UI.WebControls.TableItemStyle itemStyle = new TableItemStyle();
//AlternatingStyle.BackColor = System.Drawing.Color.LightGray;
headerStyle.BackColor = System.Drawing.Color.LightGray;
headerStyle.Font.Bold = true;
headerStyle.HorizontalAlign = System.Web.UI.WebControls.HorizontalAlign.Center;
//itemStyle.HorizontalAlign = System.Web.UI.WebControls.HorizontalAlign.Center; ;

//excel.AlternatingItemStyle.MergeWith(AlternatingStyle);
excel.HeaderStyle.MergeWith(headerStyle);
//excel.ItemStyle.MergeWith(itemStyle);
excel.GridLines = GridLines.Both;
excel.HeaderStyle.Font.Bold = true;
excel.DataSource = dt.DefaultView; //输出DataTable的内容
excel.DataBind();

//for (int i = 0; i < excel.Items.Count; i++)
//{
// //excel.Columns[3].ItemStyle.CssClass = "xlsText";
// //excel.Items[i].Cells[3].Style.Add("mso-number-format", "\"@\"");
// for (int j = 0; j < aColTxtFormat.Length; j++)
// {
// int nCol = aColTxtFormat[j];
// excel.Items[i].Cells[nCol].Attributes.Add("style", "vnd.ms-excel.numberformat:@");
// }
//}
excel.RenderControl(htmlWriter);

HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename="+FileName+".xls");
//HttpContext.Current.Response.Charset = "UTF-8";
HttpContext.Current.Response.Charset = "UTF-8";
HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.GetEncoding("UTF-8");
//HttpContext.Current.Response.ContentType=".xls/.txt/.doc";image/JPEG;text/HTML;image/GIF;vnd.ms-excel/msword
HttpContext.Current.Response.ContentType = ".xls";
HttpContext.Current.Response.Write(stringWriter.ToString());
HttpContext.Current.Response.End();

}

以上汇出Excel，没有内容的地方不显示网格线，如果要显示网格线，要增加如下内容：

HttpContext.Current.Response.ContentType = ".xls";
//这里增加如下加粗内容
HttpContext.Current.Response.End();

        Response.Write("<style type='text/css'>td{text-align:left;border:solid 1px Black;}</style>");
        Response.Write(AddExcelHead()); //显示网格线
        Response.Write(stringWriter.ToString()); 
        Response.Write(AddExcelbottom());//显示网格线
        Response.Flush();

增加两个方法：

    public static string AddExcelHead()
    {
        System.Text.StringBuilder sb = new System.Text.StringBuilder();
        sb.Append("<html xmlns:x=\"urn:schemas-microsoft-com:office:excel\">");
        sb.Append(" <head>");
        sb.Append(" <!--[if gte mso 9]><xml>");
        sb.Append("<x:ExcelWorkbook>");
        sb.Append("<x:ExcelWorksheets>");
        sb.Append("<x:ExcelWorksheet>");
        sb.Append("<x:Name></x:Name>");
        sb.Append("<x:WorksheetOptions>");
        sb.Append("<x:Print>");
        sb.Append("<x:ValidPrinterInfo />");
        sb.Append(" </x:Print>");
        sb.Append("</x:WorksheetOptions>");
        sb.Append("</x:ExcelWorksheet>");
        sb.Append("</x:ExcelWorksheets>");
        sb.Append("</x:ExcelWorkbook>");
        sb.Append("</xml>");
        sb.Append("<![endif]-->");
        sb.Append(" </head>");
        sb.Append("<body>");
        return sb.ToString();

    }

    public static string AddExcelbottom()
    {
        StringBuilder sb = new StringBuilder();
        sb.Append("</body>");
        sb.Append("</html>");
        return sb.ToString();
    }