使用响应.传输文件对于物理文件不工作

我读了很多关于这个问题的文章,我的方法是基于rickstrahl的博客 http://www.west-wind.com/weblog/posts/76293.aspx

下面是我的代码片段:

            // Get the physical Path of the file
            string docFilePath = (string)args.AttachmentKeyValues["DocFilePath"];

            // Create New instance of FileInfo class to get the properties of the file being downloaded
            FileInfo file = new FileInfo(docFilePath);

            // Checking if file exists
            if (file.Exists)
            {
                Response.ClearContent();

                Response.AddHeader("Content-Disposition", "attachment; filename=" + file.Name);


                Response.AddHeader("Content-Length", file.Length.ToString());


                Response.ContentType = ReturnExtension(file.Extension.ToLower());


                Response.TransmitFile(file.FullName);

                Response.End();
            }

看系统知道文件存在。。。它通过了回应。结束()没有错误。。。然后继续正确的应用程序。。。只是没有下载提示。

ReturnExtension方法是从另一个站点提升的(对不起,我不记得在哪里!)如下

    string ReturnExtension(string fileExtension)
    {
        // In the long run this should go in a class
        switch (fileExtension)
        {
            case ".htm":
            case ".html":
            case ".log":
                return "text/HTML";
            case ".txt":
                return "text/plain";
            case ".doc":
                return "application/ms-word";
            case ".tiff":
            case ".tif":
                return "image/tiff";
            case ".asf":
                return "video/x-ms-asf";
            case ".avi":
                return "video/avi";
            case ".zip":
                return "application/zip";
            case ".xls":
            case ".csv":
                return "application/vnd.ms-excel";
            case ".gif":
                return "image/gif";
            case ".jpg":
            case "jpeg":
                return "image/jpeg";
            case ".bmp":
                return "image/bmp";
            case ".wav":
                return "audio/wav";
            case ".mp3":
                return "audio/mpeg3";
            case ".mpg":
            case "mpeg":
                return "video/mpeg";
            case ".rtf":
                return "application/rtf";
            case ".asp":
                return "text/asp";
            case ".pdf":
                return "application/pdf";
            case ".fdf":
                return "application/vnd.fdf";
            case ".ppt":
                return "application/mspowerpoint";
            case ".dwg":
                return "image/vnd.dwg";
            case ".msg":
                return "application/msoutlook";
            case ".xml":
            case ".sdxl":
                return "application/xml";
            case ".xdp":
                return "application/vnd.adobe.xdp+xml";
            default:
                return "application/octet-stream";
        }
    }