WPF - Prism - how to pass parameters to Drawer's ViewModel

Question

This is a sample .xaml code that I have, I'm using DrawerHost Control from MaterialDesignInXamlToolkit

<UserControl 
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    d:DataContext="{d:DesignInstance viewModels:UserControlViewModel}"
    mc:Ignorable="d"
    xmlns:materialDesign="http://materialdesigninxaml.net/winfx/xaml/themes">
    
    <materialDesign:DrawerHost IsRightDrawerOpen="{Binding IsDrawerOpen}" OpenMode="Default">
        <materialDesign:DrawerHost.RightDrawerContent>
            <views:RightDrawerView />
        </materialDesign:DrawerHost.RightDrawerContent>
            <!-- Main Content -->
    </materialDesign:DrawerHost>
</UserControl>

RightDrawerViewModel will be set to be the DataContext of RightDrawerView via Prism's ViewModelLocationProvider.

My Question: When setting IsDrawerOpen to true, how can UserControlViewModel pass parameters to RightDrawerViewModel? as RightDrawerViewModel is not called via Prism's methods (regionManager?.RequestNavigate, dialogService?.ShowDialog).

Answer 1

If you want to pass parameters, you can either RequestNavigate instead of setting IsDrawerOpen (which needs a region and an custom RegionAdapter for the DrawerHost) or you create a service known to both the view model that wants to open the drawer and the drawer's view model and put all data there before setting IsDrawerOpen.

A third option is to create a new DrawerViewModel when you want to open the drawer and assign it to a property on the parent view model and bind it to the drawer's content's data context. Also, remove IsDrawerOpen and replace it either with a style or a converter that observe the view model-property on the parent.

I'd go for the first option only if I were forced to go view first, otherwise always prefer the third one. The second's ugly and presented for completeness only.