c# object.Dispose() or object = null

Question

Hi I have an object has is Disposable and I would like to know what is better:

this.object.Dispose();

or

this.object = null;

or

this.object.Dispose();
this.object = null;

Answer 1

Dispose is better, even more better approach would be to use the object inside the using block and let the framework dispose it.

For: this.object.Dispose(); vs this.object = null;

Setting the object to null may result in leaving out un-managed resources un-disposed. The whole object of having IDisposable is to make sure that un-managed resources are disposed after their usage.

See: IDisposable - MSDN

The primary use of this interface is to release unmanaged resources. The garbage collector automatically releases the memory allocated to a managed object when that object is no longer used. However, it is not possible to predict when garbage collection will occur. Furthermore, the garbage collector has no knowledge of unmanaged resources such as window handles, or open files and streams.

Answer 2

您只需要Dispose对象 - 您不需要将其设置为null ，除非有其他代码检查空值并做出适当的响应。

Answer 3

Dispose is not better or worse than setting to null. They serve different purposes.

• Set it to null to free the reference to that object so that the garbage collector can collect it. Please keep in mind that this might not have any effect if there are other references, from other objects, to it. Scopes play a major role here (remember closures, static object references, event delegates, etc).
• Call Dispose() if the developer implemented IDisposable on the object. I see the IDisposable interface as a "developer contract" which allows us to see "hey, this object cleans after itself but also provides a public method to explicitly clean it!".

Because, if implemented correctly , the finalizer of the object should call the Dispose() method, most of the times you don't need to call it explicitly. As soon as there are no references to the object, the finalizer method is called by the garbage collector and consequently the Dispose method.

Answer 4

object.Dispose() or object = null

What is dispose? Any type that implements IDisposable has this method normally (though you can write your own public method).

public class Test:IDisposable
{
    public void Dispose()
    {
           //release resources here managed and unmanaged
    }
}

Now as you have implemented IDisposable so the best way is

using (Test t = new Test())
{
}

by doing this in using block framework will take care of all the resources. and you don't need to worry. And even if you the finalizer method on the object should be calling Dispose() for you

Though alternatively you can also do

Test t = new Test();
t.Dispose();

now what about setting it null?

Test t = new Test();
t = null; 

The object it referenced is no longer accessible and can now be garbage-collected (managed resources). You have to handle the un-managed resources yourself.