如何创建使用类似于在C＃中使用的配置文件的扩展方法

Question

I am trying to create a method that looks like the following when used:

Dialog (var d = new MyDialog())
{
    d.DoSomethingToAVisibleDialogThatAppearedInTheDialog(); //Call
}

Like "using", it would handle the destructor, but I want to add more stuff to Dialog, which would handle my IDialog interface.

Answer 1

You could created a class like the following:

class DisposableWrapper<T> : where T : IDisposable {
    T _wrapped;
    private bool _disposed;
    public DisposableWrapper(T wrapped) {
        _wrapped = wrapped;
    }
    public T Item {
        get { return _wrapped; }
    }
    public ~DisposableWrapper()
    {
        Dispose(false);
        GC.SuppressFinalize(this);
    }
    public void Dispose() {
        Dispose(true);
    }
    protected virtual void Dispose(bool disposing)
    {
        if (_disposed) return;
        if (disposing) {
            _disposed = true;             
            ((IDisposable)_wrapped).Dispose();
            // do extra stuff
        }
    }
}

And then use it like so:

using (var wrapper = new DisposableWrapper(new Dialog()) {
    Dialog d = wrapper.Item;
    // do stuff
}

Answer 2

using is a language feature, and specific to IDisposable . It cannot be extended directly for different semantics. What you're trying would basically be adding a new feature to the language, which is not possible.

The best option is typically to provide an action, ideally in a generic method with a new() constraint.

public static void Dialog<T>(Action<T> action) where T: IDialog, new()
{
    var d = new T();
    try
    {
        action(d);
    }
    finally
    {
       var idialog = d as IDialog;
       if (idialog != null)
       {
           idialog.Dispose(); // Or whatever IDialog method(s) you want
       }
    }
}

You could then do:

Dialog(d => d.DoSomethingToAVisibleDialogThatAppearedInTheDialog());

Answer 3

I wrote up a class that does this called ResourceReleaser<T> .

Typical usage:

public class StreamPositionRestorer : ResourceReleaser<long>
{
    public StreamPositionRestorer(Stream s) : base(s.Position, x => s.Seek(x)) { }
}

the end result of this example is that when you do this:

using (var restorer = new StreamPositionRestorer(stm)) {
    // code that mucks with the stream all it wants...
}
// at this point the stream position has been returned to the original point