Do you need to dispose of objects and set them to null, or will the garbage collector clean them up when they go out of scope?

Do you need to dispose of objects and set them to null?

Why do some people use the `Finalize` method over the `Dispose` method? 

In what situations would you use the `Finalize` method over the `Dispose` method and vice versa?

Finalize vs Dispose

Something like:

    using (IDisposable disposable = GetSomeDisposable())
    {
        //.....
        //......
        return Stg();
    }

I believe it is not a proper place for a return statement, is it?


returning in the middle of a using block

DataSet and DataTable both implement IDisposable, so, by conventional best practices, I should call their Dispose() methods.

However, from what I&#39;ve read so far, DataSet and DataTable don&#39;t actually have any unmanaged resources, so Dispose() doesn&#39;t actually do much.

Plus, I can&#39;t just use `using(DataSet myDataSet...)` because DataSet has a collection of DataTables.

So, to be safe, I&#39;d need to iterate through myDataSet.Tables, dispose of each of the DataTables, then dispose of the DataSet.

So, is it worth the hassle to call Dispose() on all of my DataSets and DataTables?

**Addendum:**

For those of you who think that DataSet should be disposed:
In general, the pattern for disposing is to use `using` or `try..finally`, because you want to guarantee that Dispose() will be called.

However, this gets ugly real fast for a collection.  For example, what do you do if one of the calls to Dispose() thrown an exception?  Do you swallow it (which is &quot;bad&quot;) so that you can continue on to dispose the next element?

Or, do you suggest that I just call myDataSet.Dispose(), and forget about disposing the DataTables in myDataSet.Tables? 

Should I Dispose() DataSet and DataTable?

The .NET [IDisposable Pattern](http://msdn.microsoft.com/en-us/library/system.idisposable.aspx) *implies* that if you write a finalizer, and implement IDisposable, that your finalizer needs to explicitly call Dispose.
This is logical, and is what I&#39;ve always done in the rare situations where a finalizer is warranted.

However, what happens if I just do this:

    class Foo : IDisposable
    {
         public void Dispose(){ CloseSomeHandle(); }
    }

and don&#39;t implement a finalizer, or anything. Will the framework call the Dispose method for me?

Yes I realise this sounds dumb, and all logic implies that it won&#39;t, but I&#39;ve always had 2 things at the back of my head which have made me unsure.

1. Someone a few years ago once told me that it would in fact do this, and that person had a very solid track record of &quot;knowing their stuff.&quot;

2. The compiler/framework does other &#39;magic&#39; things depending on what interfaces you implement (eg: foreach, extension methods, serialization based on attributes, etc), so it makes sense that this might be &#39;magic&#39; too. 

While I&#39;ve read a lot of stuff about it, and there&#39;s been lots of things implied, I&#39;ve never been able to find a **definitive** Yes or No answer to this question.

Will the Garbage Collector call IDisposable.Dispose for me?

Start with these simple classes...
----------------------------------
Let&#39;s say I have a simple set of classes like this: 

    class Bus
    {
        Driver busDriver = new Driver();
    }

    class Driver
    {
        Shoe[] shoes = { new Shoe(), new Shoe() };
    }

    class Shoe
    {
        Shoelace lace = new Shoelace();
    }

    class Shoelace
    {
        bool tied = false;
    }

A `Bus` has a `Driver`, the `Driver` has two `Shoe`s, each `Shoe` has a `Shoelace`. All very silly.  

Add an IDisposable object to Shoelace
------------------------------------
Later I decide that some operation on the `Shoelace` could be multi-threaded, so I add an `EventWaitHandle` for the threads to communicate with. So `Shoelace` now looks like this:

    class Shoelace
    {
        private AutoResetEvent waitHandle = new AutoResetEvent(false);
        bool tied = false;
        // ... other stuff ..
    }

Implement IDisposable on Shoelace
---------------------------------
But now [Microsoft&#39;s FxCop][1] will complain: *&quot;Implement IDisposable on &#39;Shoelace&#39; because it creates members of the following IDisposable types: &#39;EventWaitHandle&#39;.&quot;*

Okay, I implement `IDisposable` on `Shoelace` and my neat little class becomes this horrible mess:

    class Shoelace : IDisposable
    {
        private AutoResetEvent waitHandle = new AutoResetEvent(false);
        bool tied = false;
        private bool disposed = false;

        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        ~Shoelace()
        {
            Dispose(false);
        }

        protected virtual void Dispose(bool disposing)
        {
            if (!this.disposed)
            {
                if (disposing)
                {
                    if (waitHandle != null)
                    {
                        waitHandle.Close();
                        waitHandle = null;
                    }
                }
                // No unmanaged resources to release otherwise they&#39;d go here.
            }
            disposed = true;
        }
    }

Or (as pointed out by commenters) since `Shoelace` itself has no unmanaged resources, I might use the simpler dispose implementation without needing the `Dispose(bool)` and Destructor:

    class Shoelace : IDisposable
    {
        private AutoResetEvent waitHandle = new AutoResetEvent(false);
        bool tied = false;

        public void Dispose()
        {
            if (waitHandle != null)
            {
                waitHandle.Close();
                waitHandle = null;
            }
            GC.SuppressFinalize(this);
        }
    }


Watch in horror as IDisposable spreads
--------------------------------------
Right that&#39;s that fixed. But now FxCop will complain that `Shoe` creates a `Shoelace`, so `Shoe` must be `IDisposable` too. 

And `Driver` creates `Shoe` so `Driver` must be `IDisposable`.
And `Bus` creates `Driver` so `Bus` must be `IDisposable` and so on.

Suddenly my small change to `Shoelace` is causing me a lot of work and my boss is wondering why I need to checkout `Bus` to make a change to `Shoelace`.

The Question
------------
How do you prevent this spread of `IDisposable`, but still ensure that your unmanaged objects are properly disposed?


  [1]: https://en.wikipedia.org/wiki/FxCop

How do you prevent IDisposable from spreading to all your classes?

My root problem is that when `using` calls `Dispose` on a `StreamWriter`, it also disposes the `BaseStream` (same problem with `Close`).

I have a workaround for this, but as you can see, it involves copying the stream. Is there any way to do this without copying the stream?

The purpose of this is to get the contents of a string (originally read from a database) into a stream, so the stream can be read by a third party component.   
**NB**: I cannot change the third party component.

    public System.IO.Stream CreateStream(string value)
    {
        var baseStream = new System.IO.MemoryStream();
        var baseCopy = new System.IO.MemoryStream();
        using (var writer = new System.IO.StreamWriter(baseStream, System.Text.Encoding.UTF8))
        {
            writer.Write(value);
            writer.Flush();
            baseStream.WriteTo(baseCopy); 
        }
        baseCopy.Seek(0, System.IO.SeekOrigin.Begin);
        return baseCopy;
    }

Used as

    public void Noddy()
    {
        System.IO.Stream myStream = CreateStream(&quot;The contents of this string are unimportant&quot;);
        My3rdPartyComponent.ReadFromStream(myStream);
    }

Ideally I&#39;m looking for an imaginary method called `BreakAssociationWithBaseStream`, e.g.

    public System.IO.Stream CreateStream_Alternate(string value)
    {
        var baseStream = new System.IO.MemoryStream();
        using (var writer = new System.IO.StreamWriter(baseStream, System.Text.Encoding.UTF8))
        {
            writer.Write(value);
            writer.Flush();
            writer.BreakAssociationWithBaseStream();
        }
        return baseStream;
    }

Is there any way to close a StreamWriter without closing its BaseStream?

I have created a custom WPF user control which is intended to be used by a third party. My control has a private member which is disposable, and I would like to ensure that its dispose method will always get called once the containing window/application is closed. However, UserControl is not disposable. 

I tried implementing the IDisposable interface and subscribing to the Unloaded event but neither get called when the host application closes. MSDN says that the Unloaded event may not be raised at all. And it might also be triggered more than once, that is when user changes theme. 

If at all possible, I don&#39;t want to rely on consumers of my control remembering to call a specific Dispose method.

     public partial class MyWpfControl : UserControl
     {
         SomeDisposableObject x;

         // where does this code go?
         void Somewhere() 
         {
             if (x != null)
             {
                 x.Dispose();
                 x = null;
             }

         }
     }

The only solution I have found so far is to subscribe to the Dispatcher&#39;s ShutdownStarted event. Is this a reasonable approach?

    this.Dispatcher.ShutdownStarted += Dispatcher_ShutdownStarted;

Disposing WPF User Controls

I want to trigger a task to run on a background thread. I don&#39;t want to wait on the tasks completion.

In .net 3.5 I would have done this:

    ThreadPool.QueueUserWorkItem(d =&gt; { DoSomething(); });

In .net 4 the TPL is the suggested way. The common pattern I have seen recommended is:

    Task.Factory.StartNew(() =&gt; { DoSomething(); });

However, the [`StartNew()`][1] method returns a [`Task`][2] object which implements `IDisposable`. This 
seems to be overlooked by people who recommend this pattern. The MSDN documentation on the [`Task.Dispose()`][3] method says:

&gt; &quot;Always call Dispose before you release your last reference to the Task.&quot;

You can&#39;t call dispose on a task until it is completed, so having the main thread wait and call dispose would defeat the point of doing on a background thread in the first place. There also doesn&#39;t seem to be any completed/finished event that could be used for cleanup.

The MSDN page on the Task class doesn&#39;t comment on this, and the book &quot;Pro C#2010...&quot; recommends the same pattern and makes no comment on task disposal.

I know if I just leave it the finalizer will catch it in the end, but is this going to come back and bite me when I&#39;m doing lots of fire &amp; forget tasks like this and the finalizer thread gets overwhelmed?

So my questions are: 

 - Is it acceptable to not call `Dispose()` on the `Task` class in this case? And if so, why and are there risks/consequences?
 - Is there any documentation that discusses this? 
 - Or is there an appropriate way of disposing of the `Task` object that I&#39;ve missed?
 - Or is there another way of doing fire &amp; forget tasks with the TPL?


  [1]: http://msdn.microsoft.com/en-us/library/dd321439.aspx
  [2]: http://msdn.microsoft.com/en-us/library/system.threading.tasks.task.aspx
  [3]: http://msdn.microsoft.com/en-us/library/dd270681.aspx

Is it considered acceptable to not call Dispose() on a TPL Task object?

I&#39;ve the following code

    using(MemoryStream ms = new MemoryStream())
    {
         //code
         return 0;
    }

The `dispose()` method is called at the end of `using` statement braces `}` right? Since I  `return` before the end of the `using` statement, will the `MemoryStream` object be disposed properly? What happens here?

What happens if i return before the end of using statement? Will the dispose be called?

When would I implement IDispose on a class as opposed to a destructor?  I read [this article][1], but I&#39;m still missing the point.  

My assumption is that if I implement IDispose on an object, I can explicitly &#39;destruct&#39; it as opposed to waiting for the garbage collector to do it.  Is this correct?

Does that mean I should always explicitly call Dispose on an object?  What are some common examples of this?


  [1]: http://www.dotnetspider.com/resources/1382-Understanding-IDisposable-pattern.aspx

What is the difference between using IDisposable vs a destructor in C#?

Is there a method, or some other light-weight way, to check if a reference is to a disposed object?

P.S. - This is just a curiousity (sleep well, not in production code).  Yes, I know I can catch the `ObjectDisposedException` upon trying to access a member of the object.

How does one tell if an IDisposable object reference is disposed?

&gt; **Possible Duplicate:**  
&gt; [How does one tell if an IDisposable object reference is disposed?](https://stackoverflow.com/questions/192206/how-does-one-tell-if-an-idisposable-object-reference-is-disposed)  

&lt;!-- End of automatically inserted text --&gt;

Is there a method to check if object has been disposed different then

    try
    {
        myObj.CallRandomMethod();
    } catch (ObjectDisposedException e)
    {
        // now I know object has been disposed
    }

In my case I&#39;m using `TcpClient` class that has `Close()` method which disposes object and this can happen in piece of code I don&#39;t have control of. In this case I would like to have better solution then catching exception.

How to check if object has been disposed in C#

I am studying how garbage collector works in c#. I am confused over the use of `Destructor`, `Dispose` and `Finalize` methods. 

As per my research and understandings, having a Destructor method within my class will tell the garbage collector to perform the garbage collection in the way mentioned in the destructor method which cannot be called explicitly on the instances of the class. 

The `Dispose` method is meant to provide the user to control the garbage collection.  The `Finalize` method frees the resources used by the class, but not the object itself. 

I am not sure if I understand it the right way. Please clarify the doubts. Any further links or guides are welcome.


Difference between destructor, dispose and finalize method

It&#39;s recently been pointed out to me that various Linq extension methods (such as `Where`, `Select`, etc) return an &lt;code&gt;IEnumerable&amp;lt;T&amp;gt;&lt;/code&gt; that also happens to be &lt;code&gt;IDisposable&lt;/code&gt;. The following evaluates to &lt;code&gt;True&lt;/code&gt;

    new int[2] {0,1}.Select(x =&gt; x*2) is IDisposable

Do I need to dispose of the results of a &lt;code&gt;Where&lt;/code&gt; expression? 

Whenever I call a method returning `IEnumerable&lt;T&gt;`, am I (potentially) accepting responsibility for calling dispose when I&#39;ve finished with it? 



Do I need to consider disposing of any IEnumerable&lt;T&gt; I use?

I am getting this warning from FxCop:

&gt; &quot;&#39;RestartForm&#39; contains field &#39;RestartForm.done&#39; that is of IDisposable type: &#39;ManualResetEvent&#39;. Change the Dispose method on &#39;RestartForm&#39; to call Dispose or Close on this field.&quot;

Ok, I understand what this means and why this is what needs to be done... Except `System.Windows.Forms.Form` doesn&#39;t allow you to override either `.Close()` or `.Dispose()`, so what to do? Currently I&#39;m running with this solution:

        private void RestartForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            done.Set();
            done.Close();
        }

Which works as intended for my application... But FxCop still shows this message. Am I covered and can I safely ignore it, or is there another way I should be doing this?

How do I extend a WinForm&#39;s Dispose method?

I thought the GC would call Dispose eventually if your program did not but that you should call Dispose() in your program just to make the cleanup deterministic.

However, from my little test program, I don&#39;t see Dispose getting called at all....

    public class Test : IDisposable
    {
        static void Main(string[] args)
        {
            Test s = new Test();
            s = null;
            GC.Collect();
            Console.ReadLine();
        }
    
        public Test()
        {
            Console.WriteLine(&quot;Constructor&quot;);
        }
    
        public void Dispose()
        {
            Console.WriteLine(&quot;Dispose&quot;);
        }
    }

// Output is just &quot;Constructor&quot;, I don&#39;t get &quot;Dispose&quot; as I would expect.  What&#39;s up?

**EDIT:** Yes, I know I should call Dispose() - I do follow the standard pattern when using disposable objects.  My question arises because I&#39;m trying to track down a leak in somebody elses code, which is managed C++ (another layer of complexity that would be the good subject of another thread).

Does garbage collector call Dispose()?

What follows is a typical dispose pattern example:

     public bool IsDisposed { get; private set; }
    
      #region IDisposable Members
    
      public void Dispose()
      {
        Dispose(true);
        GC.SuppressFinalize(this);
      }
    
      protected virtual void Dispose(bool disposing)
      {
        if (!IsDisposed)
        {
          if (disposing)
          {
            //perform cleanup here
          }
    
          IsDisposed = true;
        }
      }
    
      ~MyObject()
      {
        Dispose(false);
      }

I understand what dispose does, but what I don&#39;t understand is why you would want to call dispose(false) in the destructor? If you look at the definition it would do absolutely nothing, so why would anyone write code like this? Wouldn&#39;t it make sense to just *not* call dispose from the destructor at all?

Why call dispose(false) in the destructor?

This was a telephone interview question I had: Is there a time when Dispose will not be called on an object whose scope is declared by a using block?

My answer was no - even if an exception happens during the using block, Dispose will still be called.

The interviewer disagreed and said if `using` is wrapped in a `try`-`catch` block then Dispose will not be called by the time you enter the catch block.

This goes contrary to my understanding of the construct, and I haven&#39;t been able to find anything that backs up the interviewers point of view. Is he correct or might I have misunderstood the question?


Is there a situation in which Dispose won&#39;t be called for a &#39;using&#39; block?

Can I use this approach efficiently?

    using(SqlCommand cmd = new SqlCommand(&quot;GetSomething&quot;, new SqlConnection(Config.ConnectionString))
    {
        cmd.Connection.Open();
        // set up parameters and CommandType to StoredProcedure etc. etc.
        cmd.ExecuteNonQuery();
    }

My concern is : Will the Dispose method of the SqlCommand (which is called when exiting the using block) close the underlying SqlConnection object or not?


Does SqlCommand.Dispose close the connection?

I have a class which implements UserControl. In .NET 2005, a Dispose method is automatically created in the MyClass.Designer.cs partial class file that looks like this:

      protected override void Dispose(bool disposing)
      {
         if (disposing &amp;&amp; (components != null))
         {
            components.Dispose();
         }
         base.Dispose(disposing);
      }


If I want to add my own Dispose functionality, where would I put it? Since this file is generated, I don&#39;t want to add code here and risk it getting blown away.


How do I add Dispose functionality to a C# UserControl?

Starting from the following situation:

    public interface ISample
    {
    }
    
    public class SampleA : ISample
    {
       // has some (unmanaged) resources that needs to be disposed
    }
    
    public class SampleB : ISample
    {
       // has no resources that needs to be disposed
    }

The class SampleA should implement the interface IDisposable for releasing resources.
You could solve this in two ways:

**1. Add the required interface to the class SampleA:**

    public class SampleA : ISample, IDisposable
    {
       // has some (unmanaged) resources that needs to be disposed
    }

**2. Add it to the interface ISample and force derived classes to implement it:**

    public interface ISample : IDisposable
    {
    }

If you put it into the interface, you force any implementation to implement IDisposable even if they have nothing to dispose. On the other hand, it is very clear to see that the concrete implementation of an interface requires a dispose/using block and you don&#39;t need to cast as IDisposable for cleaning up. There might be some more pros/cons in both ways... why would you suggest to use one way preferred to the other?



Declare IDisposable for the class or interface?

I&#39;m working in C# and my workplace has some code standards. One of them is that each event handler we connect (such as `KeyDown`) must be disconnected in the `Dispose` method. Is there any good reason for that?

All Dispose Solutions on Gang of Coders

Total of 23 Dispose Solutions