Context locators

Dock assigns dockable.Context when a layout is initialized or loaded if the dockable does not already have a context. The objects are resolved through two properties on IFactory: ContextLocator and DefaultContextLocator.

ContextLocator dictionary

ContextLocator is a Dictionary<string, Func<object?>> mapping an identifier to a factory method. Each entry returns the object that becomes dockable.Context (often used as a view DataContext) for the dockable with the same Id. Populate this dictionary before calling InitLayout, including when you initialize a layout loaded with an IDockSerializer.

public override void InitLayout(IDockable layout)
{
    ContextLocator = new Dictionary<string, Func<object?>>
    {
        ["Document1"] = () => new DocumentViewModel(),
        ["Tool1"] = () => new Tool1ViewModel(),
    };

    base.InitLayout(layout);
}

During InitDockable the factory looks up the dockable Id in ContextLocator and assigns the returned object to dockable.Context when it is still null. If the id is not found, it falls back to DefaultContextLocator. Empty ids skip the lookup entirely, so ensure you set Id on dockables you want resolved.

DefaultContextLocator fallback

DefaultContextLocator is a Func<object?> invoked when ContextLocator has no entry for the requested identifier. Use it to provide a common fallback or to integrate with a dependency injection container.

DefaultContextLocator = () => _services.GetService<MainViewModel>();

When GetContext cannot resolve a specific non-empty id it will call this delegate. If it returns null, the dockable keeps its existing Context (often null).

DockControl default context

When DockControl.InitializeFactory is true, the control assigns DefaultContextLocator for you and returns the value of DockControl.DefaultContext. This is a convenient way to supply a shared fallback without touching the factory:

var dockControl = new DockControl
{
    DefaultContext = new MainViewModel(),
    InitializeFactory = true
};

If you want to configure DefaultContextLocator yourself, disable InitializeFactory or assign your locator after the control initializes.

Why it matters

Dockable views often rely on dockable.Context (directly or via templates) to function correctly. When loading a layout that references custom documents or tools, the factory must be able to recreate those view models. Register each type in ContextLocator and provide a default via DefaultContextLocator so that unknown ids do not break the layout.

These locators work alongside DockableLocator and HostWindowLocator which resolve dockable instances and host windows. Ensure all locators are populated before deserializing layouts or initializing new ones.

For a high level overview of the factory API see the Advanced guide and Reference guide.