The solution ended up being really simple and close to what I had thought should be possible:

In the parent component:

<ShoppingList ShoppingList="@appState.ShoppingList"/>
<Totals Total="@appState.Total"/>

@code {
    appState.AddToList(new item{
        amount = 1,
        name = "beef"
    });
}

and then in the components themselves you add a parameter:

@code {
    [Parameter]
    public List<AppState.Item> ShoppingList{ get; set; }
}

I have an AppState class in my project that keeps track of a list. I also have a component that shows the list to the user, as well as another component that shows some other data by making some calculations using the list.

When I add to the list I want both the visual list component and the calculation component to update, but depending on from which component I add an item it updates either only that component or neither (if I add from the parent).

Is there a way to tell a selection of components that they have to re-render? I managed to get it working when I instantiate the list OnInitialized but when it doesn’t re-render when I make changes.

Some psuedo-code of what I was thinking of:

<ShoppingList @bind="appState.ShoppingList"/>
<Totals @bind="appState.ShoppingList"/>

@code {
    appState.AddToList(new item{
        amount = 1,
        name = "beef"
    });
}

I had hoped that this would make the components update when the list changed but sadly that is not the case.