Memory Management

Shell objects and services often have to deal with unmanaged resources that need cleanup when they are no longer used. For instance, Windows shell objects internally maintain a system-specified PIDL reference.

The shell types used in this product are all disposable, and it's a best practice to manually dispose them after use. This helps keep memory from building up until those objects would later be automatically finalized.

Warning

The shell object framework can be used independently of shell UI controls, and shell objects can even be shared across multiple shell UI controls. Thus, it's not really possible for us to know when to automatically dispose shell objects and services, and the objects must rely on you the developer to trigger disposal.

Shell Objects

A root shell object can be set to controls like ShellTreeListBox when its RootShellFolder property is set directly, or its RootShellFolderParsingName or RootSpecialFolderKind properties are set. In these cases, the shell object hierarchy likely has unmanaged resources being maintained.

When the UI control is no longer in use, the object that was set to the RootShellFolder property directly or indirectly should be disposed, and that property should be set to null.

Shell Services

A WindowsShellService instance is set, by default, to the DefaultShellService property of controls like ShellTreeListBox. The WindowsShellService doesn't create any unmanaged resources until it's actually used, but it's important to dispose the service.

When the UI control is no longer in use, the object that was set to the DefaultShellService property should be disposed, and that property should be set to null.

Dispose Helper Methods on UI Controls

Both the ShellTreeListBox and ShellListView controls have a DisposeShellInstances helper method that takes the recommended actions for you.

This method takes whichever IShellObject was set as the root shell folder and disposes it, while also resetting the control's RootShellFolder property back to null. Additionally, it takes the current DefaultShellService instance and disposes it, while also setting the DefaultShellService property to null. These steps should help ensure that unmanaged resources aren't memory-leaked.

Important