Resource Acquisition is Initialization in C#

Resource Acquisition Is Initialization (RAII) is a pattern I grew to love when working in C++. It is perfectly suited for resource management such as matching all those pesky new's and delete's. One of my goals was to limit the explicit deallocation statements I had to write. Often these statements became victims of run-time control flow changes (i.e. exceptions, unhappy path) or development-time code refactoring.

The beauty of RAII is realized by tying your resource creation (acquisition) to the construction (initialization) of a class instance. Then bind the resource deallocation to the destruction of that instance. That is well and good in a language with strong destructor semantics like C++, but languages like C# that run on garbage-collecting runtimes don't provide the same instance lifetime guarantees.

Here is a class and sample that combines a few features of C# to provide an RAII-like solution:

using System;

namespace RAII { public class DisposableDelegate : IDisposable { private Action dispose;

    public DisposableDelegate(Action dispose)
    {
        if (dispose == null)
        {
            throw new ArgumentNullException("dispose");
        }

        this.dispose = dispose;
    }

    public void Dispose()
    {
        if (this.dispose != null)
        {
            Action d = this.dispose;
            this.dispose = null;
            d();
        }
    }
}

class Program
{
    static void Main(string\[\] args)
    {
        Console.Out.WriteLine("Some resource allocated here.");

        using (new DisposableDelegate(() => Console.Out.WriteLine("Resource deallocated here.")))
        {
            Console.Out.WriteLine("Resource used here.");

            throw new InvalidOperationException("Test for resource leaks.");
        }
    }
}

}

The output of this program is:

Some resource allocated here. Resource used here.

Unhandled Exception: System.InvalidOperationException: Test for resource leaks. at RAII.Program.Main(String[] args) in c:\Dev\RAII\RAII\Program.cs:line 40 Resource deallocated here.

Code without fear!

--Don

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