为什么当我“使用”时我的 FileStream 对象被释放？ BinaryReader 对象？

发布于 2024-10-21 13:28:34 字数 421 浏览 8 评论 0原文

考虑以下函数：

    private int GetSomethingFromFile(FileStream fs) 
    {
        using (BinaryReader br = new BinaryReader(fs))
        {
            fs.Seek(0, SeekOrigin.Begin);
            return br.ReadInt32();
        }
    }

FileStream 对象作为参数传入，并使用 using 语句声明 BinaryReader。当我尝试使用该 FileStream 对象时，在调用此函数后，它会抛出 System.ObjectDisposeException。为什么 FileStream 对象与 BinaryReader 对象一起被处理？

原文

Consider the following function:

    private int GetSomethingFromFile(FileStream fs) 
    {
        using (BinaryReader br = new BinaryReader(fs))
        {
            fs.Seek(0, SeekOrigin.Begin);
            return br.ReadInt32();
        }
    }

A FileStream object is passed in as a parameter and a BinaryReader is declared with a using statement. When I try to use that FileStream object, after calling this function, it throws a System.ObjectDisposedException. Why is that FileStream object being disposed of along with the BinaryReader object?

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几味少女 2024-10-28 13:28:34

这是一个非常好的问题，我不知道为什么决定应该是这样的，但遗憾的是它被记录为这样：

BinaryReader 类

关闭：关闭当前读取器和底层流。

如果您查看此答案问题如何在 .NET 中“分叉”流？然后你会看到他引用了一个名为 MiscUtilJon Skeet 所写的 a> 可以用来环绕流以防止其被关闭。

您可以像这样使用它（对于您的示例）：

private int GetSomethingFromFile(FileStream fs) 
{
    using (var wrapper = new NonClosingStreamWrapper(fs))
    using (BinaryReader br = new BinaryReader(wrapper))
    {
        fs.Seek(0, SeekOrigin.Begin);
        return br.ReadInt32();
    }
}

It is a very good question, and I don't know why it was decided that this was how it should be, but alas it is documented to be this way:

BinaryReader class

Close: Closes the current reader and the underlying stream.

If you check out this answer to the question How do I “fork” a Stream in .NET? then you'll see that he refers to a class called NonClosingStreamWrapper in a library called MiscUtil that @Jon Skeet has written that you can use to wrap around the stream to prevent it from being closed.

You would use it like this (for your example):

private int GetSomethingFromFile(FileStream fs) 
{
    using (var wrapper = new NonClosingStreamWrapper(fs))
    using (BinaryReader br = new BinaryReader(wrapper))
    {
        fs.Seek(0, SeekOrigin.Begin);
        return br.ReadInt32();
    }
}

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