从组件派生并正确实现 IDisposable

Question

我有一个 Visual Studio 2008 C# .NET 2.0 CF 项目，其中有一个派生自 Component 的抽象类。从那个类，我派生了几个具体的类（如下面的例子）。 但是，当我退出 Form 时，虽然调用了 Form 的 Dispose() 成员并调用了 components.Dispose()，但我的组件永远不会被释放。

谁能建议我如何修复这个设计？

public abstract class SomeDisposableComponentBase : Component
{
    private System.ComponentModel.IContainer components;

    protected SomeDisposableComponentBase()
    {
        Initializecomponent();
    }

    protected SomeDisposableComponentBase(IContainer container)
    {
        container.Add(this);
        Initializecomponent();
    }

    private void InitializeComponent()
    {
        components = new System.ComponentModel.Container();
    }

    protected abstract void Foo();

    #region IDisposable Members
    bool disposed_;

    /// Warning 60 CA1063 : Microsoft.Design : Ensure that 'SomeDisposableComponentBase.Dispose()' is declared as public and sealed.*
    public void Dispose()
    {
        // never called
        Dispose(true);
        GC.SuppressFinalize(this);
    }

    protected virtual void Dispose(bool disposing)
    {
        // never called
         if (!disposed_)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            disposed_ = true;
        }
        base.Dispose(disposing);
    }
    #endregion    
}

public SomeDisposableComponent : SomeDisposableComponentBase
{
    public SomeDisposableComponent() : base()
    {
    }

    public SomeDisposableComponent(IContainer container) : base(container)
    {
    }

    protected override void Foo()
    {
        // Do something...
    }

    protected override void Dispose(bool disposing)
    {
        // never called
        base.Dispose(disposing);
    }
}

public partial class my_form : Form
{
    private SomeDisposableComponentBase d_;

    public my_form()
    {
        InitializeComponent();
        if (null == components)
            components = new System.ComponentModel.Container();

        d_ = new SomeDisposableComponent(components);
    }

    /// exit button clicked
    private void Exit_Click(object sender, EventArgs e)
    {
        this.Close();
    }

    /// from the my_form.designer.cs
    protected override void Dispose(bool disposing)
    {
        if (disposing && (components != null))
        {
            // this function is executed as expected when the form is closed
            components.Dispose();
        }
        base.Dispose(disposing);
    }
}

*我注意到 FX-Cop 在这里给了我一个提示。但是，如果我尝试将该函数声明为密封，则会收到错误消息：

error CS0238: 'SomeDisposableComponentBase.Dispose()' cannot be sealed because it is not an override

声明该函数为覆盖会导致：

'SomeDisposableComponentBase.Dispose()': cannot override inherited member 'System.ComponentModel.Component.Dispose()' because it is not marked virtual, abstract, or override

谢谢， 保罗H

Answer 1

SomeDisposableComponentBase 应该覆盖 Component.Dispose(Boolean)。

您还需要删除 SomeDisposableComponentBase.Dispose() 方法（不带参数）because it hides the Component.Dispose implementation，因此它们被视为不同的方法，具体取决于您声明变量的方式：

using (Component component = new SomeDisposableComponent()) {
    // Calls Component.Dispose upon exiting the using block
}

using (SomeDisposableComponentBase component = new SomeDisposableComponent()) {
    // Calls SomeDisposableComponentBase.Dispose upon existing the using block
}

Answer 2

发生的事情是编译器将 SomeDisposableComponentBase 上的 Dispose 方法解释为

new public void Dispose() 
{ 
    // never called 
    Dispose(true); 
    GC.SuppressFinalize(this); 
} 

这不是覆盖，它为类层次结构中的现有名称提供了新的语义。所以，实际上您正在创建一个与 Component.Dispose 不同的新 Dispose 方法。

查看Implementing Finalize and Dispose to Clean Up Unmanaged Resources 文章以获取有关如何实现 IDisposable.Dispose 方法的官方指南。