DataGrid行添加事件

Question

I know... this question was being asked a lot... but always with the same answer "put your logic in the viewmodel".

But in this example I have to put the logic in the view because I have to measure the size of each datagrid in my view every time the row count of one of them is changing. The problem is... in my viewmodel I don´t have access to the datagrid, so I can´t measure anything. And in my view I can´t get a response that the row count has changed.

Someone got an idea how I know in the view that a row was added or deleted in a datagrid? It is a custom datagrid with a customtemplate btw. maybe that is going to help somehow?

Answer 1

You have an ObservableCollection binded to the DataGrid , right? And you have a ViewModel (which contains that ObservableCollection ) as the DataContext of the View . You may subscribe to the CollectionChanged event of the ObservableCollection within your view (you can access your ViewModel from your view, because it is the View.DataContext ).

Eg

(this.DataContext as ViewModel).YourCollection
    .CollectionChanged += (s, e) => { /* logic */ };

It slightly violates MVVM. If this is an absolutely custom control then you already receive the events from the ObservableCollection (because you need to update the UI) so you can handle this there.

Another approach I can think is to use some kind of Mediator pattern, eg Messenger in MVVMLight.