为什么asp.net下载不起作用？

Question

我正在使用此代码下载图像，即我将具有扩展名的图像名称存储在数据库中，并在此处获取。

此代码不会引发错误，但不会下载任何内容。 为什么呢？

try {
    if (e.CommandName == "Download")
    {
        string ImgPath = Convert.ToString(r["Attachment"]);
        //string ImgName = r["ComplaintDetailID"].ToString() + "-" + r["LetterNo"].ToString() + "-" + DateTime.Now.ToString("ddMMyyyyhhmmss");

        //string filePath = ImgName + ".jpg";
        string fullFilePath = Server.MapPath("~/SiteImages/CMS/" + ImgPath);
        Response.Clear();
        Response.ClearHeaders();
        Response.ClearContent();
        Response.AddHeader("Content-Disposition", "attachment; filename=" + Path.GetFileName(fullFilePath));
        Response.ContentType = ContentType;
        Response.TransmitFile(fullFilePath); //downloads file
        Response.Flush();

        //FileInfo file = new FileInfo(fullFilePath);
        //file.Delete(); //deletes file after downloading
    }
}
catch (Exception ex)
{
    ResultLabel.ResultLabelAttributes(ex.Message, ProjectUserControls.Enums.ResultLabel_Color.Red);
}
finally 
{
    ResultPanel.Controls.Add(ResultLabel);
}

更新：

我试过了，但没有用。

 if (e.CommandName == "Download")
            {
                string ImgPath = Convert.ToString(r["Attachment"]);
                //string ImgName = r["ComplaintDetailID"].ToString() + "-" + r["LetterNo"].ToString() + "-" + DateTime.Now.ToString("ddMMyyyyhhmmss");


                        //string filePath = ImgName + ".jpg";
                        MemoryStream m = new MemoryStream();
                        File.OpenRead(ImgPath).CopyTo(m);
                        m.WriteTo(Response.OutputStream);

                        string fullFilePath = Server.MapPath("~/SiteImages/CMS/" + ImgPath);
                        Response.Clear();
                        Response.ClearHeaders();
                        Response.ClearContent();
                        Response.AddHeader("Content-Disposition", "attachment; filename=" + Path.GetFileName(fullFilePath));
                        Response.ContentType = ContentType;
                        Response.TransmitFile(fullFilePath); //downloads file
                        Response.Flush();

                        //FileInfo file = new FileInfo(fullFilePath);
                        //file.Delete(); //deletes file after downloading
            }

Answer 1

使用以下代码创建流

MemoryStream m = new MemoryStream();
File.OpenRead(ImgPath ).CopyTo(m);
m.WriteTo(Response.OutputStream);

Answer 2

您使用TransmitFile的方向正确。 检查这一行：

Response.ContentType = ContentType;

看起来您要将ContentType设置为页面的默认值。

尝试明确指定它：

Response.ContentType = "image/jpeg";