C#导出xls,word,图片及样式问题

public void ExportControl(System.Web.UI.Control source, string DocumentType, string filename)
{
//设置Http的头信息,编码格式
HttpContext.Current.Response.Buffer = true;
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.ClearContent();
HttpContext.Current.Response.ClearHeaders();
if (DocumentType.ToLower() == "excel")
{
//Excel
HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(filename + ".xls", System.Text.Encoding.UTF8));
HttpContext.Current.Response.ContentType = "application/ms-excel";
}
else if (DocumentType.ToLower() == "word")
{
//Word
HttpContext.Current.Response.AppendHeader("Content-Disposition", "attachment;filename=" + HttpUtility.UrlEncode(filename + ".doc", System.Text.Encoding.UTF8));
HttpContext.Current.Response.ContentType = "application/ms-word";
}
HttpContext.Current.Response.Charset = "UTF-8";
HttpContext.Current.Response.HeaderEncoding=System.Text.Encoding.UTF8;
HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.UTF8;
//关闭控件的视图状态
source.Page.EnableViewState = false;
//初始化HtmlWriter
System.IO.StringWriter writer = new System.IO.StringWriter();
System.Web.UI.HtmlTextWriter htmlWriter = new System.Web.UI.HtmlTextWriter(writer);
source.RenderControl(htmlWriter);
//输出
HttpContext.Current.Response.Write(writer.ToString());
HttpContext.Current.Response.End();
}
    //方法ExportControl(System.Web.UI.Control source, string DocumentType,string filename)中
    //第一个参数source表示导出的页面或控件名,当为data