Do you know when to implement IDisposable?

Last updated by William Liebenberg almost 2 years ago.See history

If you access unmanaged resources (e.g. files, database connections etc.) in a class, you should implement IDisposable and overwrite the Dispose method to allow you to control when the memory is freed.  If not, this responsibility is left to the garbage collector to free the memory when the object containing the unmanaged resources is finalized. This means the memory will be unnecessarily consumed by resources which are no longer required, which can lead to inefficient performance and potentially running out of memory altogether.

public class MyClass
   private File myFile = File.Open(...); // This is an unmanaged resource

//elsewhere in project:
private void useMyClass()
  var myClass = new MyClass();
  Here we are using an unmanaged resource without disposing of it, meaning it will hang around in memory unnecessarily until the garbage collector finalizes it

Figure: Bad example - Using unmanaged resources without disposing of them when we are done

public class MyClass : IDisposable
  private File myFile = new File.Open(...); // This is an unmanaged resource

  public void Dispose()
    myFile.Dispose(); // Here we dispose of the unmanaged resource
    GC.SuppressFinalize(this); // Preventing a redundant garbage collector finalize call

Figure: Good example - Implementing IDisposable allows you to dispose of the unmanaged resources deterministically to maximize efficiency

Now we can use the using statement to automatically dispose the class when you are finished with it.:

private void useClass()
  using (var myClass = new MyClass())
    // do stuff with myClass here...
  }  // myClass.Dispose() is automatically run at the end of the using block

Figure: Good example - With the using statement, the unmanaged resources are disposed of as soon as we are finished with them

See here for more details.

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