如何使用ASP.NET MVC 5和实体框架下载MP3文件

debugcn 发表于 Dev

奥托洛伊

我已经成功完成了上传位-将MP3文件上传到了我的SQL Server，但是在下载文件时需要帮助...。我使用以下代码上传MP3文件

public ActionResult Create([Bind(Include = "ID,Artist,Album")] TrackUpload trackUpload, HttpPostedFileBase upload)
{
    try
    {
        if (ModelState.IsValid)
        {
            if (upload != null && upload.ContentLength > 0)
            {
                var song = new File
                {
                    FileName = System.IO.Path.GetFileName(upload.FileName),
                    FileType = FileType.Songs,
                    ContentType = upload.ContentType
                };
                using (var reader = new System.IO.BinaryReader(upload.InputStream))
                {
                    song.Content = reader.ReadBytes(upload.ContentLength);
                }
                trackUpload.Files = new List<File> { song };
            }
            db.TrackUploads.Add(trackUpload);
            db.SaveChanges();
            return RedirectToAction("Index");
        }
    }

    catch (RetryLimitExceededException /* dex */)
    {

        ModelState.AddModelError("", "Cant save changes.");
    }
    return View(trackUpload);
}

运行正常，这意味着文件存储在数据库中，现在如何使用实体框架从sql db下载MP3文件

山本哲也

要从MVC控制器下载MP3文件，请确保将MIME类型设置FileContentResult为或（有关详细信息audio/mp3，请参见http://filext.com/file-extension/MP3）。audio/mpeg3audio/x-mpeg3

这是定义文件下载方案的简单控制器代码：

/*
 *  assume Id becomes file ID key to download
 *  this code provides simple download function by returning FileContentResult with proper MIME type
 */
public FileContentResult DownloadFile(int Id) 
{
    // assume FileContext is your file list DB context with FileName property (file name + extension, e.g. Sample.mp3)
    using (FileContext db = new FileContext())
    {
        var download = db.TrackUploads.Where(x => x.ID == Id).SingleOrDefault();
        if (download != null) 
        {
            // remove this line if you want file download on the same page
            Response.AddHeader("content-disposition", "inline; filename=" + download.FileName);
            return File(download.FileName, "audio/mp3");
        }
        else
        {
            return null;
        }
    }
}

附录

要在下载之前从文件扩展名获取MIME类型，此代码部分可能适用：

if (download != null) 
{
    String mimeType = MimeMapping.GetMimeMapping(download.FileName);
    ...
    // other tasks
    ...
    return File(download.FileName, mimeType);
}

参考：使用Entity FrameWork从sql db查看和下载文件（对MP3扩展进行了调整）

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