IDisposable通常用于利用using语句，并利用一种简单的方法对托管对象进行确定性清理。

public class LoggingContext : IDisposable {
    public Finicky(string name) {
        Log.Write("Entering Log Context {0}", name);
        Log.Indent();
    }
    public void Dispose() {
        Log.Outdent();
    }

    public static void Main() {
        Log.Write("Some initial stuff.");
        try {
            using(new LoggingContext()) {
                Log.Write("Some stuff inside the context.");
                throw new Exception();
            }
        } catch {
            Log.Write("Man, that was a heavy exception caught from inside a child logging context!");
        } finally {
            Log.Write("Some final stuff.");
        }
    }
}

IDisposable/using组合除了主要用作控制系统资源生命周期的方法（完全被Ian的精彩回答所涵盖）外，还可以用于确定（关键）全局资源的状态变化范围：控制台、线程、进程、任何全局对象（如应用程序实例）。

我写了一篇关于这种模式的文章：http://pragmateek.com/c-scope-your-global-state-changes-with-idisposable-and-the-using-statement/

它说明了如何以可重用和可读的方式保护一些常用的全局状态：控制台颜色、当前线程区域性、Excel应用程序对象财产。。。

给定的代码示例不是IDisposable用法的好示例。字典清除通常不应转到Dispose方法。字典项在超出范围时将被清除和处理。需要IDisposable实现来释放一些内存/处理程序，即使它们超出范围也不会释放/释放。

下面的示例显示了IDisposable模式的一个很好的示例，其中包含一些代码和注释。

public class DisposeExample
{
    // A base class that implements IDisposable. 
    // By implementing IDisposable, you are announcing that 
    // instances of this type allocate scarce resources. 
    public class MyResource: IDisposable
    {
        // Pointer to an external unmanaged resource. 
        private IntPtr handle;
        // Other managed resource this class uses. 
        private Component component = new Component();
        // Track whether Dispose has been called. 
        private bool disposed = false;

        // The class constructor. 
        public MyResource(IntPtr handle)
        {
            this.handle = handle;
        }

        // Implement IDisposable. 
        // Do not make this method virtual. 
        // A derived class should not be able to override this method. 
        public void Dispose()
        {
            Dispose(true);
            // This object will be cleaned up by the Dispose method. 
            // Therefore, you should call GC.SupressFinalize to 
            // take this object off the finalization queue 
            // and prevent finalization code for this object 
            // from executing a second time.
            GC.SuppressFinalize(this);
        }

        // Dispose(bool disposing) executes in two distinct scenarios. 
        // If disposing equals true, the method has been called directly 
        // or indirectly by a user's code. Managed and unmanaged resources 
        // can be disposed. 
        // If disposing equals false, the method has been called by the 
        // runtime from inside the finalizer and you should not reference 
        // other objects. Only unmanaged resources can be disposed. 
        protected virtual void Dispose(bool disposing)
        {
            // Check to see if Dispose has already been called. 
            if(!this.disposed)
            {
                // If disposing equals true, dispose all managed 
                // and unmanaged resources. 
                if(disposing)
                {
                    // Dispose managed resources.
                    component.Dispose();
                }

                // Call the appropriate methods to clean up 
                // unmanaged resources here. 
                // If disposing is false, 
                // only the following code is executed.
                CloseHandle(handle);
                handle = IntPtr.Zero;

                // Note disposing has been done.
                disposed = true;

            }
        }

        // Use interop to call the method necessary 
        // to clean up the unmanaged resource.
        [System.Runtime.InteropServices.DllImport("Kernel32")]
        private extern static Boolean CloseHandle(IntPtr handle);

        // Use C# destructor syntax for finalization code. 
        // This destructor will run only if the Dispose method 
        // does not get called. 
        // It gives your base class the opportunity to finalize. 
        // Do not provide destructors in types derived from this class.
        ~MyResource()
        {
            // Do not re-create Dispose clean-up code here. 
            // Calling Dispose(false) is optimal in terms of 
            // readability and maintainability.
            Dispose(false);
        }
    }
    public static void Main()
    {
        // Insert code here to create 
        // and use the MyResource object.
    }
}

如果要立即删除，请使用非托管内存。

See:

马歇尔.AllocHGlobalMarshal.FreeHGlobal公司编组.仓库结构

如果有的话，我希望代码的效率比不使用它时要低。

调用Clear（）方法是不必要的，如果Dispose不这样做，GC可能不会这么做。。。

是的，这段代码完全是多余和不必要的，它不会让垃圾回收器做任何它不会做的事情（即，一旦MyCollection的实例超出范围），尤其是.Clear（）调用。

对编辑的回答：有点。如果我这样做：

public void WasteMemory()
{
    var instance = new MyCollection(); // this one has no Dispose() method
    instance.FillItWithAMillionStrings();
}

// 1 million strings are in memory, but marked for reclamation by the GC

在内存管理方面，它的功能与此相同：

public void WasteMemory()
{
    var instance = new MyCollection(); // this one has your Dispose()
    instance.FillItWithAMillionStrings();
    instance.Dispose();
}

// 1 million strings are in memory, but marked for reclamation by the GC

如果您真的真的需要立即释放内存，请调用GC.Collect（）。内存将在需要时释放。