如何在 C# 中处理托管和非托管对象？

Question

全部。我从来没有使用过析构函数也没有处理过，所以这对我来说是新的。我的任务是做一个 class，它有析构函数和处置方法，它有一个自动增量的 UInt64 Id 属性，和一个必须的静态 Dictionary<UInt64,MyClass>通过 Id 引用 live MyClass.

实例

在搜索了如何正确使用它们之后，这就是我最终做的事情：

public class MyClass : IDisposable
{
    private static Object Lock = new Object();
    private static Dictionary<UInt64, MyClass> LiveInstances = new Dictionary<UInt64, MyClass>();

    public UInt64 Id { get; private set; }

    public MyClass()
    {
        lock (Lock)
        {
            var newId = IncrementalId();
            if (newId == 0)
            {
                throw new ArgumentException("Reached MAX VAL");
            }
            Id = newId;
            LiveInstances.Add(Id, this);
        }
    }

    ~MyClass()
    {
       CleanUpNativeResources();
    }     

    public void Dispose()
    {
        lock (Lock)
        {
            CleanUpManagedResources();
            CleanUpNativeResources();
            GC.SuppressFinalize(this);
        }
    }

    protected virtual void CleanUpManagedResources()
    {
        LiveInstances.Remove(Id);

    }
    protected virtual void CleanUpNativeResources()
    {

    }

    private static UInt64 IncrementalId()
    {
        for (ulong i = 0; i <= Convert.ToUInt64(LiveInstances.Count) ; i++)
        {
            if (i != UInt64.MaxValue && !LiveInstances.ContainsKey(i + 1))
            {
                return i+1;
            }
        }
        return 0;
    }
}

现在，我的问题是 如何处理对象？ 无论我是否尝试查找处理对象的示例，我都会找到类似这个：

 // Code to dispose the managed resources of the class
 Console.WriteLine("Object disposed");

提前致谢。

Answer 1

托管资源将在某个时间点由垃圾收集器自动处理。非托管资源类似于文件句柄，通过 Windows API 调用 returns 必须手动释放的 Windows 句柄获得。您没有任何需要手动处理的东西。如果您不释放这些句柄，它们将在程序运行期间保持分配状态，但所有具有非托管资源的 .Net classes 都提供 Finalizer（见下文）以确保他们通常会在某个时候被释放。

（但如果您正在编写自己的文件处理程序 class 并且忘记在任何地方释放文件句柄，文件将保持打开状态直到您的程序退出。）

通常这种非托管资源会在两个地方被释放：

Dispose() 方法。这应该是您处理非托管资源的正常方式。

终结器。这是最后的手段机制。如果 class 有终结器，垃圾收集器在清理死对象时会调用它。如果程序员忘记调用 Dispose()，任何具有非托管资源的 class 都应该有一个终结器来清理。

使用的基本 Dispose 模式是这样的：

class MyObject : IDisposable
{
    //indicates if dispose has already been called
    //private bool _disposed = false;

    //Finalize method for the object, will call Dispose for us
    //to clean up the resources if the user has not called it
    ~MyObject()
    {
        //Indicate that the GC called Dispose, not the user
        Dispose(false);
    }

    //This is the public method, it will HOPEFULLY but
    //not always be called by users of the class
    public void Dispose()
    {
        //indicate this was NOT called by the Garbage collector
        Dispose(true);

        //Now we have disposed of all our resources, the GC does not
        //need to do anything, stop the finalizer being called
        GC.SupressFinalize(this);
    }

    private void Dispose(bool disposing)
    {
        //Check to see if we have already disposed the object
        //this is necessary because we should be able to call
        //Dispose multiple times without throwing an error
        if (!disposed)
        {
            if (disposing)
            {
                //clean up managed resources
                components.Dispose();
            }

            //clear up any unmanaged resources - this is safe to
            //put outside the disposing check because if the user
            //called dispose we want to also clean up unmanaged
            //resources, if the GC called Dispose then we only
            //want to clean up managed resources
        }
    }
}

如何在 C# 中处理托管和非托管对象？

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