close or dispose

Question

StreamReader class has both close and dispose method. I want to know which method to call to clean up all resources.

If making use of using block, I think it will call its dispose method. Will it be enough to clean up all the resources.

Answer 1

The using block will call Dispose() on the StreamReader instance. Generally speaking, if a type is IDisposable, you should put it in using scope.

EDIT: If you look at the Close() implementation of StreamReader using Reflector, you will see that it's calling Dispose(true). So if you're not using the using scope, calling Close() manually would be the same as calling Dispose() in this particular case.

protected override void Dispose(bool disposing)
{
    try
    {
        if ((this.Closable && disposing) && (this.stream != null))
        {
            this.stream.Close();
        }
    }
    finally
    {
        if (this.Closable && (this.stream != null))
        {
            this.stream = null;
            this.encoding = null;
            this.decoder = null;
            this.byteBuffer = null;
            this.charBuffer = null;
            this.charPos = 0;
            this.charLen = 0;
            base.Dispose(disposing);
        }
    }
}

Answer 2

We all know System.IO.StreamReader is not the only .NET 4.0+ class that implements IDisposable and a Close() method. For the case of StreamReader in this question, the source code shows that the base class TextReader.Close(), TextReader.Dispose() both run the same lines of code. You can also see in the code that TextReader.Dispose() is the implementation for when you call StreamReader.Dispose() (because StreamReader doesn't override that method overload signature of Dispose).

So a call to StreamReader.Dispose() will run this inherited line of code, which calls the protected override method StreamReader.Dispose(disposing: true) and so will StreamReader.Close() call StreamReader.Dispose(disposing: true). So for the case of StreamReader, Close() and Dispose() do happen to run the same lines of code.

A more general, non-class-specific answer to the question of Close() or Dispose()?, might be to note that Microsoft has fairly clear documentation on implementing IDisposable and the Dispose pattern. A quick read is enough to show you that implementing a Close() method is not a requirement of the Dispose pattern.

imho the reason for finding the method Close() on so many classes that implement IDisposable, is the result of convention, not requirement.

Someone commented

Close and Dispose - which to call?

An example of another class that implements IDisposable with the Dispose pattern, and has a Close() method. Does Close() run the same code as Dispose() in this case? I haven't looked at the source code, but I'd say not necessarily.

Answer 3

Use Dispose via a using block to guarantee that clean-up happens.

Use Close if you finish with the object considerably before the end of the using block, to be as prompt as possible in releasing any resources.

The two will hence work hand-in-hand, though the latter can be redundant if you are going to reach the end of the block in a few nanoseconds anyway.

Answer 4

The using block is all that you need.

Answer 5

If you want further information about using, take a look here

Using

Quote from site:

The using statement allows the programmer to specify when objects that use resources should release them. The object provided to the using statement must implement the IDisposable interface. This interface provides the Dispose method, which should release the object's resources.

Answer 6

There appears to be some concern about whether Dispose actually does its job properly.

Essentially - you can be fairly certain that anything in the BCL(Base Class Library) which implements IDisposable will tidy itself up properly when dispose is called - such as when a using statement goes out of scope.

If there were issues with streams not being closed they would have been picked up by now - you can trust IDisposable. It's when you're using other libraries that you rely on the Dispose implementation.