在 ASP.NET 中实现文件下载时如何处理我的文件流? [英] How do I dispose my filestream when implementing a file download in ASP.NET?

问题描述

我有一个 DocumentGenerator 类，它包装了一个 MemoryStream.所以我在类上实现了 IDisposable.

我不知道如何/在哪里处理它.

这是我当前的代码，它在 MVC 中执行文件下载:

using (DocumentGenerator dg = DocumentGenerator.OpenTemplate(path)){/* 一些文档操作DocumentGenerator 在这里...*/返回文件(dg.GetDocumentStream()，文本/纯文本"，文件名)；}

此错误是因为在控制器完成之前关闭/处置了流.在这种情况下，我如何确保我的资源得到妥善处置?

我目前对 IDisposable 的实现只是处理了 MemoryStream.我知道这不是一个正确的实现，我只是将它用作测试.我可以在这里做些不同的事情来使其发挥作用吗?

public void Dispose(){_ms.Dispose();_ms = 空；}

解决方案

您不需要处理流.它将由 FileStreamResult.WriteFile方法.本课程的代码摘录:

public FileStreamResult(Stream fileStream, string contentType) : base(contentType){如果(文件流 == 空){throw new ArgumentNullException("fileStream");}this.FileStream = fileStream;}protected override void WriteFile(HttpResponseBase response){流 outputStream = response.OutputStream;使用 (this.FileStream){字节[]缓冲区=新字节[0x1000]；而(真){int count = this.FileStream.Read(buffer, 0, 0x1000);如果(计数== 0){返回;}outputStream.Write(buffer, 0, count);}}}

注意using.当您从控制器调用 File(dg.GetDocumentStream(), "text/plain", filename) 时，这会调用构造函数，该构造函数将流存储到在呈现期间处置的公共属性中.>

结论:您无需担心使用 dg.GetDocumentStream() 处理获取的流.

I have a class DocumentGenerator which wraps a MemoryStream. So I have implemented IDisposable on the class.

I can't see how/where I can possibly dispose it though.

This is my current code, which performs a file download in MVC:

using (DocumentGenerator dg = DocumentGenerator.OpenTemplate(path))
{
    /* some document manipulation with the 
       DocumentGenerator goes here ...*/

    return File(dg.GetDocumentStream(), "text/plain", filename);
}

This errors as the stream is closed/disposed before the controller has finished with it. How can I make sure my resources are properly disposed in this situation?

EDIT: My implementation of IDisposable at the moment just disposes the MemoryStream. I know it's not a proper implementation, I just used it as a test. Is there something different I could do here to make it work?

public void Dispose()
{
    _ms.Dispose();
    _ms = null;
}

解决方案

You don't need to dispose the stream. It will be disposed by the FileStreamResult.WriteFile method. Code excerpt from this class:

public FileStreamResult(Stream fileStream, string contentType) : base(contentType)
{
    if (fileStream == null)
    {
        throw new ArgumentNullException("fileStream");
    }
    this.FileStream = fileStream;
}

protected override void WriteFile(HttpResponseBase response)
{
    Stream outputStream = response.OutputStream;
    using (this.FileStream)
    {
        byte[] buffer = new byte[0x1000];
        while (true)
        {
            int count = this.FileStream.Read(buffer, 0, 0x1000);
            if (count == 0)
            {
                return;
            }
            outputStream.Write(buffer, 0, count);
        }
    }
}

Notice the using. When you call File(dg.GetDocumentStream(), "text/plain", filename) from your controller this invokes the constructor which stores the stream into a public property which is disposed during the rendering.

Conclusion: you don't need to worry about disposing the stream obtain with dg.GetDocumentStream().

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