将IDisposable ( Disposable模式)实现为服务(类成员)

Question

Disposable模式是在每个类的基础上重新实现的模式。所以，我在寻找一种方法来概括它。几年前我遇到的问题是，即使您将其实现为类本身，也不能同时从Disposable实现和其他类派生对象(C#不支持多继承)。

问题是，如何使Disposable模式得以实现，从而不需要在每个实现IDisposable?的类中显式地编写它

下面是Visual为您生成的标准可处理模式(VS 2015)。

public class TestClass : IDisposable {
    #region IDisposable Support

    private bool disposedValue = false; // To detect redundant calls

    protected virtual void Dispose(bool disposing) {
        if (!disposedValue) {
            if (disposing) {
                // TODO: dispose managed state (managed objects).
            }

            // TODO: free unmanaged resources (unmanaged objects) and override a finalizer below.
            // TODO: set large fields to null.

            disposedValue = true;
        }
    }

    // TODO: override a finalizer only if Dispose(bool disposing) above has code to free unmanaged resources.
    // ~DisposeTest() {
    //   // Do not change this code. Put cleanup code in Dispose(bool disposing) above.
    //   Dispose(false);
    // }

    // This code added to correctly implement the disposable pattern.
    public void Dispose() {
        // Do not change this code. Put cleanup code in Dispose(bool disposing) above.
        Dispose(true);
        // TODO: uncomment the following line if the finalizer is overridden above.
        // GC.SuppressFinalize(this);
    }

    #endregion
}

Answer 1

我的实施

这就是我想出的解决方案。

public class DisposeService<T> where T : IDisposable {
    private readonly T _disposee;
    public Action<T> ManagedAction { get; set; }
    public Action<T> UnmanagedAction { get; set; }

    public DisposeService(T disposee, Action<T> managedAction = null, Action<T> unmanagedAction = null) {
        _disposee = disposee;
        ManagedAction = managedAction;
        UnmanagedAction = unmanagedAction;
    }

    private bool _isDisposed;

    public void Dispose(bool isDisposing) {
        if (_isDisposed) return;
        if (isDisposing && ManagedAction != null) {
            ManagedAction(_disposee);
        }
        var hasUnmanagedAction = UnmanagedAction != null;
        if (hasUnmanagedAction) {
            UnmanagedAction(_disposee);
        }
        _isDisposed = true;
        if (isDisposing && hasUnmanagedAction) {
            GC.SuppressFinalize(_disposee);
        }
    }
}

这个类允许您为实现DisposableService<>的类创建一个IDisposable成员。下面是一个示例，说明如何在只有托管资源的情况下使用它。

public class TestClass : IDisposable {
    protected readonly DisposeService<TestClass> DisposeService;
    private readonly SafeHandle _handle;

    public TestClass() {
        DisposeService = new DisposeService<TestClass>(this, ps => { if (_handle != null) _handle.Dispose(); });
        _handle = new SafeFileHandle(IntPtr.Zero, true);
    }

    public void Dispose() {
        DisposeService.Dispose(true);
    }
}

它是如何工作的

• DisposeService将在对象的Dispose上运行它的Dispose。
• DisposeService的dispose将运行您在初始化(或在派生类中更新)时提供的托管和非托管操作。
• 如果提供了一个GC.SuppressFinalize，UnmanagedAction将自动运行。
• 始终确保创建DisposableService<>作为构造函数的第一个操作。

因此，下面是一个在非托管资源中使用此服务的示例。

public class TestClass : IDisposable {
    protected readonly DisposeService<TestClass> DisposeService;
    private readonly SafeHandle _handle;

    public TestClass() {
        DisposeService = new DisposeService<TestClass>(this,
            ps => { if (_handle != null) _handle.Dispose(); },
            ps => { /* Free unmanaged resources here */ });
        _handle = new SafeFileHandle(IntPtr.Zero, true);
    }

    public void Dispose() {
        DisposeService.Dispose(true);
    }

    ~TestClass() {
        DisposeService.Dispose(false);
    }
}

以及从上述类生成派生类的示例。

public class TestClassDerived : TestClass, IDisposable {
    private readonly SafeHandle _derivedHandle;

    public TestClassDerived() {
        // Copy the delegate for the base's managed dispose action.
        var baseAction = DisposeService.ManagedAction;
        // Update the managed action with new disposes, while still calling the base's disposes.
        DisposeService.ManagedAction = ps => {
            if (_derivedHandle != null) {
                _derivedHandle.Dispose();
            }
            baseAction(ps);
        };
        _derivedHandle = new SafeFileHandle(IntPtr.Zero, true);
    }
}

很容易挤柠檬。保留对基委托的引用，并将其作为派生类委托的一部分进行调用。

总的来说，应该更干净，然后管理程序的区域，这是微软自2005年以来一直提供的.

编辑：，我认为在构造函数中传递的'this‘可能是个问题。但是，情况似乎并非如此：Is it a bad practice to pass "this" as an argument?只需记住在操作中放置空检查，这样就不会尝试释放空的东西。:-)