using引用的问题

2012-01-25 08:31:46 287 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

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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。

...全文

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切换为时间正序

宝_爸 2012-01-25

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GC.Collect();
释放的是托管资源，而不是非托管资源。

骑着蜗牛去爬山 2012-01-25

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[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 2012-01-25

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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 2012-01-25

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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 2012-01-25

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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

using引用的问题

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