Question

我有一个非关闭流类，它包含在带有二进制阅读器的using块中，但由于某种原因，当块结束时，我的非关闭流仍然关闭。

流定义为：

internal class NonClosingStream : Stream, IDisposable
{
    private Stream baseStream;

    public NonClosingStream(Stream baseStream)
    {
        this.baseStream = baseStream;
    }

    public override bool CanRead{ get { return baseStream.CanRead; } }
    public override bool CanSeek{ get { return baseStream.CanSeek; } }
    public override bool CanWrite { get { return baseStream.CanWrite; } }

    public override void Flush()
    {
        baseStream.Flush();
    }

    public override long Length { get { return baseStream.Length; } }

    public override long Position
    {
        get { return baseStream.Position; }
        set { baseStream.Position = value; }
    }

    public override int Read(byte[] buffer, int offset, int count)
    {
        return baseStream.Read(buffer, offset, count);   
    }

    public override long Seek(long offset, SeekOrigin origin)
    {
        return baseStream.Seek(offset, origin);
    }

    public override void SetLength(long value)
    {
        baseStream.SetLength(value);
    }

    public override void Write(byte[] buffer, int offset, int count)
    {
        baseStream.Write(buffer, offset, count);
    }

    public override void Close()
    {
        // Disconnects from base stream, but does not close it
        this.baseStream = null;
    }

    void IDisposable.Dispose()
    {
        // Disconnects from base stream, but does not close it
        this.baseStream = null;
    }
}

，读取块如下所示：

public T Deserialize<T>(Stream stream)
{
    using (NonClosingStream nonClosingStream = new NonClosingStream(stream))
    using (BinaryReader reader = new BinaryReader(nonClosingStream, Encoding.ASCII, true))
    {
        // Read the type name, then convert it to an actual type
        String typeName = reader.ReadString();
        Type graphType = AvailableTypes.GetType(typeName);

        // If a deserializer for this type already exists, use it.
        if (deserializerFunctions.ContainsKey(graphType))
        {
            return (T)deserializerFunctions[graphType](reader);
        }

        // Otherwise, create one and use it
        T graph = (T)FormatterServices.GetUninitializedObject(graphType);

        typeof(ServiceSerializer).GetMethod("DeserializeObject",
                BindingFlags.NonPublic | BindingFlags.Static)

            .MakeGenericMethod(graphType)
            .Invoke(this, new Object[] { reader, graph });

        return graph;
    }
}

我做错了什么？

更新

所以我写了这个小伙伴：

static void Main()
{
    MemoryStream stream = new MemoryStream();
    using (NonClosingStream nonCloser = new NonClosingStream(stream))
    using (BinaryWriter writer = new BinaryWriter(nonCloser))
    using (BinaryReader reader= new BinaryReader(nonCloser))
    {
        writer.Write("Lorem ipsum");

        stream.Seek(0, SeekOrigin.Begin);
        String data = reader.ReadString();

        Console.WriteLine(data);
    }

    stream.Seek(0, SeekOrigin.Begin);

    using (NonClosingStream nonCloser = new NonClosingStream(stream))
    using (BinaryWriter writer = new BinaryWriter(nonCloser))
    using (BinaryReader reader = new BinaryReader(nonCloser))
    {
        writer.Write("Lorem ipsum");

        stream.Seek(0, SeekOrigin.Begin);
        String data = reader.ReadString();

        Console.WriteLine(data);
    }

    Console.ReadLine();
}

它似乎工作正常，流保持开放，就像它应该的那样。所以我认为共识是正确的。不知何故，我正在其他地方关闭流。当我弄清楚我会发布什么结果。谢谢大家。

更新

Gaaaahhh，我发现了问题所在。因此代码的工作方式是，当它对一个对象进行序列化/反序列化时，它会从表达式树中构建一个自定义的序列化程序，然后对其进行编译，以便将来的序列化更加流畅。这意味着我的代码充满了这样的东西：

Action<BinaryReader, Object> assignmentAction = delegate(BinaryReader bReader, Object oGraph)
{
    bReader.ReadByte();      // Read the next action
    bReader.ReadString();    // Read the field name
    bReader.ReadByte();      // Read the field type

    // Call the assignment lambda
    assignmentLambda(reader, deserializerFunctions[primitiveType], (T)oGraph);
};

你抓到了吗？没有？我显然也没有。让我们添加一些上下文：

private static void DeserializeObject<T>(BinaryReader reader, T graph)
{
    ...

    Action<BinaryReader, Object> assignmentAction = delegate(BinaryReader bReader, Object oGraph)
    {
        bReader.ReadByte();      // Read the next action
        bReader.ReadString();    // Read the field name
        bReader.ReadByte();      // Read the field type

        // Call the assignment lambda
        assignmentLambda(reader, deserializerFunctions[primitiveType], (T)oGraph);
    };

    ...
}

lambda从外部块关闭reader，而不是使用缓存的反序列化程序运行时提供的bReader。因此，当解串器运行时，它使用已经丢弃的二进制读取器对象而不是提供给它的新对象。我想问题不在于我关闭了流，而是我正在使用一个处理过的读者。至少这解释了为什么它会工作一次，然后第二次失败，因为它第二次依赖于缓存的反序列化器。糟糕！

谢谢大家。

Answer 1

由于您的流不会创建内部流，因此很可能外部代码会关闭您的内部流。您的代码可能是：

 NonClosingStream nonClosing;
 using(var stream = new FileStream(...))
 {
   nonClosing = new NonClosingStream(stream );
  ....
 } 
 // inner stream now closed and nonClosing will fail all operations.

Answer 2

void IDisposable.Dispose()

您的课程有两个 Dispose（）方法。你明确实施的那个。而你从Stream类继承的那个。问题是，BinaryStream不知道关于你的bean。它只知道Stream实现的那个。此外，当您使用BinaryStream（Stream）构造函数时，BinaryStream对象将承担传递的Stream对象的所有权。这意味着当它自己处理时它将处理该流。也许您现在看到问题，将调用继承的Dispose（）方法，而不是您的方法。它关闭了基本流。

这就是Stream实现Dispose模式的原因。你需要让它看起来像这样：

internal class NonClosingStream : Stream {
    protected override Dispose(bool disposing) {}
}

Answer 3

这取决于NonClosingStream类包装的流是否在其他地方引用。如果没有，那么底层流将没有引用，所以在某些时候它的终结器将关闭流。

为什么我的非关闭流仍然关闭？

3 个答案: