//相对路径下载。path: ~/DownLoad/
//<add key="DownLoadPath" value="~/DownLoad/"/>
public static bool DownLoadFile(string path, string fileName)
{
    bool result = false; 
    try
    {
        string filePath = HttpContext.Current.Server.MapPath(path + fileName);
        if (File.Exists(filePath))
        { 
            FileInfo fileInfo = new FileInfo(filePath);
            HttpContext.Current.Response.Clear();
            HttpContext.Current.Response.ClearContent();
            HttpContext.Current.Response.ClearHeaders();
            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
            HttpContext.Current.Response.AddHeader("Content-Length", fileInfo.Length.ToString());
            HttpContext.Current.Response.AddHeader("Content-Transfer-Encoding", "binary");
            HttpContext.Current.Response.ContentType = "application/octet-stream";
            HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.GetEncoding("utf-8");
            HttpContext.Current.Response.WriteFile(fileInfo.FullName);
            HttpContext.Current.Response.Flush(); 
            HttpContext.Current.Response.End();
            result = true;
        }
    }
    catch
    { 
    } 
    return result;
}
 

//物理路径下载。path: D:\DownLoad//<add key="DownLoadPath" value="D:\DownLoad\"/>
public static bool DownLoadFile(string path, string fileName)
{
    bool result = false;
    string filePath = path + fileName;
    if (File.Exists(filePath))
    { 
        try
        {
            //string filePath = HttpContext.Current.Server.MapPath(path + fileName);
            
            FileInfo fileInfo = new FileInfo(filePath);
            HttpContext.Current.Response.Clear();
            HttpContext.Current.Response.ClearContent();
            HttpContext.Current.Response.ClearHeaders();
            HttpContext.Current.Response.AddHeader("Content-Disposition", "attachment;filename=" + fileName);
            HttpContext.Current.Response.AddHeader("Content-Length", fileInfo.Length.ToString());
            HttpContext.Current.Response.AddHeader("Content-Transfer-Encoding", "binary");
            HttpContext.Current.Response.ContentType = "application/octet-stream";
            HttpContext.Current.Response.ContentEncoding = System.Text.Encoding.GetEncoding("utf-8");
            HttpContext.Current.Response.WriteFile(fileInfo.FullName);
            HttpContext.Current.Response.Flush(); 
            result = true; 
        }
        catch (Exception e)
        {
        }
        finally
        {
            HttpContext.Current.Response.End();    //解决 ThreadAbortException 异常问题

        }
    } 
    return result;
}