Is it possible to write C# so that objects are garbage collected when they fall out of scope?

c#, garbage-collection

Solution

No. In fact, you don't really want it to be garbage collected - prompting the garbage collector very frequently will reduce performance.

What you do want is to dispose of the unmanaged resources in a timely manner - and that's where `IDisposable` comes in, along with the `using` statement:

void MyFunction()
{
    using (Bitmap image = RetrieveImage())
    {
        DoSomething(image);
    }
}

That will call `image.Dispose()` as it leaves the `using` statement, whether or not `DoSomething` threw an exception.

You do have to use the extra variable though - unless you change `DoSomething` to take a `Func<Bitmap>` instead, so instead of:

void DoSomething(Bitmap image)
{
    // Code here
}
...
DoSomething(RetrieveImage());

you'd have:

void DoSomething(Func<Bitmap> imageProvider)
{
    using (Bitmap image = imageProvider())
    {
        // Code here
    }
}
...
DoSomething(() => RetrieveImage());

Note that that doesn't give the opportunity to pass in a bitmap without it being disposed - which could be a problem if you want to use it again later. Still, it's a nice technique to at least know about.

EDIT: As mbeckish has pointed out in his comments, there isn't very much benefit here over just disposing of the bitmap within `RetrieveImage`. Here's a variant on the pattern though:

public void ApplyToEachLineInFile(string file, Action<string> action)
{
    using (TextReader reader = File.OpenText(file))
    {
        string line;
        while ((line = reader.ReadLine()) != null)
        {
            action(line);
        }
    }
}

Here the "acquire and dispose" logic is encapsulated, without the caller worrying about it - but the caller can still be very flexible in terms of the complexity of logic they pass in.

Problem

For example, in the below code an 'image'object will be created and then garbage collected at some unknown point in the future ``` void MyFunction() { Bitmap image = RetrieveImage(); DoSomething(image); } ``` What about ``` void MyFunction() { DoSomething(RetrieveImage()); } ``` In this case is the object garbage collected once it moves out of scope i.e. After the end of MyFunction. If not is there somewhere to enforce this?

Original source