Resource Acquisition is Initialization in C#
- by codeWithoutFear
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
