Sometime ago there was discussion on StackOverflow about BinaryWriter implementation. As you may know BinaryWriter and all other .NET Wrtiers implement IDisposable. You also might be aware about guidance to always call Dispose. Boring… 

using(var s = File.OpenWrite("1.txt")){
    	using(var w = new StreamWriter(s)){
    		...
    	}
    }

The question is… Why? So you have Stream and it has resources to dispose. Then you have Writer… And… It does not have resources to dispose. Why to dispose then? I do not know.

So why they implement IDisposable? I think about this as a marketing for newbie developers. Most examples in MSDN looks like: 

using (var sw = new StreamWriter("1.txt")) {
    	...
    }

Without IDisposable this code will fail to close handlers to file. For me this is just leaked design of the StreamWriter.

At the end of the day, I can formulate my IDisposable usage.

By default, always call Dispose. But if you sure what are you doing - do not call!

How to ensure that call to Dispose is not required? Following is my checklist:

  1. Think about usage semantics. In most cases, this gives 90% of sure;
  2. Use .NET Reflector. It can unhide some stuff you may not aware about;
  3. Read documentation. This also can help to decide;

Anyway, add comment to the code. This will be helpful for maintainers and will reduce questions during reviews.

And remember:

  1. Dispose it contract. If one marking code with this contract, for sure he want to say something;
  2. Things changing. Behaviour of the Dispose could also change. You will have nothing to say, when your code will not work on .NET 5.0;

BTW

  1. DataSet implements IDisposable. This is because of usage in .NET Remoting and Design Time support. In addition DataTable, DataView and even DataColumn are the same. And no they do not clean data;
  2. SqlCommand and everything derived fromDbCommand. It does exactly nothing. Why it have? What resources it suppose to own?
  3. Something not expected at all - ‘SqlCommandBuilder'. What is expected Dispose do nothing notable here;
  4. Each Component implements IDisposable. Even if does not own resources. Think about WinForms BindingSource, ‘ErrorProvider';
  5. Ha!, IEnumerator<T> is also here! This is dark side!
  6. And at the end WCF Clients has "broken" IDisposable implementation;
  7. Some stuff could use, IDisposable as syntax sugar.

Enjoy! Happy coding!