Memory Management

It is important to ensure that unmanaged resources are released when they are no longer required, in order to avoid creating memory leaks. This is accomplished using the IDisposable interface. If a class creates unmanaged resources, or creates instances of classes which implement IDisposable themselves, it should implement IDisposable and release these resources in the Dispose() method. Detailed information on how to implement Dispose() can be found in Microsoft's documentation, here.

note

Classes instantiated via dependency injection that implement IDisposable will automatically have Dispose() called by Autofac once their lifetime scope has ended, so Dispose() does not need to be called explicitly for such classes.

Using Mobile's IDisposableTracker Interface

Mobile's toolkit also includes a helpful interface and extension methods to make tracking disposable resources easier: IDisposableTracker and DisposableUtilities. ComponentBase and ServiceBase already implement IDisposableTracker, so any custom components or services extending these base classes can take advantage of this functionality right away. Here is a brief example of how to use it in a new class:

public class DisposableTrackerExample: IDisposableTracker, IDisposable
{
	// Implement the IDisposableTracker interface
	public IList<IDisposable> Disposables => new List<IDisposable>();

	public DisposableTrackerExample()
	{
		// Pointer to a fictitious external unmanaged resource.
		SafeFileHandle handle = new SafeFileHandle(IntPtr.Zero, true);

		// Track the file handle in the Disposables list
		Disposables.Add(handle);
	}

	public void Dispose()
	{
		// This will dispose of the FileSafeHandle created in the constructor
		this.DisposeTrackers();
	}
}

Using DisposeTrackers() is a shortcut which is functionally identical to calling Dispose() on each IDisposable in the Disposables list.

IDisposableTracker is also used when registering commands and operations, as described here, and subscribing to events, described here.

Relevant SDK Sample

Check out the sample on the disposal pattern in VertiGIS Studio Mobile.