using引用的问题

[骑着蜗牛去爬山]

using(OleDbConnection conn=new OleDbConnection())
{
;
}
上面的代码正常,不报错
using (string s = "aa")
{
;
}
以上代码报错：“string”: using 语句中使用的类型必须可隐式转换为“System.IDisposable”
请教高手，到底什么时候用using ，什么时候不用using？
如果我自定义一个类（继承IDisposable），应该怎么写？
请高手帮帮我这个菜鸟，祝所有人新年快乐。

[宝_爸]

提示的很清楚了，只有实现了“System.IDisposable”的类才能用到using中。

你自己的类，只要实现了“System.IDisposable”接口就可以了。

using System;
using System.ComponentModel;

// The following example demonstrates how to create
// a resource class that implements the IDisposable interface
// and the IDisposable.Dispose method.

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.
    }
}

以上代码来自msdn:
http://msdn.microsoft.com/en-us/library/system.idisposable.dispose.aspx

[骑着蜗牛去爬山]

public class a:IDisposable

{
public int aa(int i)
{
return i;
}
}
提示错误 1 “a”不会实现接口成员“System.IDisposable.Dispose()”。
为什么呢？

[宝_爸]

你的实现IDisposable接口中定义的方法啊

public class a:IDisposable

{
public int aa(int i)
{
return i;
}

public void Dispose()
{
释放你的非托管资源。
}

}

[骑着蜗牛去爬山]

[Quote=引用 3 楼 findcaiyzh 的回复:]
你的实现IDisposable接口中定义的方法啊

public class a:IDisposable

{
public int aa(int i)
{
return i;
}

public void Dispose()
{
释放你的非托管资源。
}

}
[/Quote]
3Q
还有个小问题
public void Dispose()
{
GC.Collect();
}
除了这种方法还有什么方法释放非托管资源？

[宝_爸]

GC.Collect();
释放的是托管资源，而不是非托管资源。