WPF MVVM Can i use model from view

Question

I am still new to MVVM/WPF, in my control, i create a grid and when user clicks on a row, i want it to do something. Currently, i have in my code executes some code on the view. Is this okay? since the view need to access data from the model, or how can i fully separate the view and the model?

Currently, i have this...

// our View Window
public partial class MarketPriceView : UserControl
{
    public MarketPriceView()
    {
        InitializeComponent();      
    }

    private void OHLCChart_Click(object sender, RoutedEventArgs e)
    {
        // MarketPriceGrid is our model
        var cell = GridData.SelectedItem as MarketPriceGrid;
        string prod = cell.ProdCode;

        // do something with prod ...
    }
}

and my XAML i have a datagrid

<DataGrid x:Name="GridData" ItemsSource="{Binding MarketPriceGrid}">
  <DataGrid.ContextMenu>
    <ContextMenu>
      <MenuItem Header="OHLC Chart" Click="OHLCChart_Click"/>
     </ContextMenu>
    </DataGrid.ContextMenu>
    ...
</DataGrid>

Is this OK? Or how should i go about doing it without breaking the MVVM pattern?

it is not a MVVM implementation, when you don't have ViewModels. you can't break something what doesn't exist — ASh, Oct 11 '19 at 09:32

score 0 · Accepted Answer · answered Oct 11 '19 at 10:02

The OHLCChart_Click event handler in the view should be replaced by an ICommand property of the view model that you bind to:

<MenuItem Header="OHLC Chart" Command="{Binding ChartCommand"}/>

Please refer to this blog post for more information about how to handle events in MVVM.

You should also bind the SelectedItem property of the DataGrid to a source property of the view model:

<DataGrid x:Name="GridData" ItemsSource="{Binding MarketPriceGrid}"
          SelectedItem="{Binding TheSelectedItem}">

You will then have direct access to the currently selected item in the Execute method of the command in the view model:

_clickCommand = new DelegateCommand<object>(
        (s) => { /* do something with this.TheSelectedItem */ }, //Execute
        (s) => true //CanExecute
        );

This way, you move your application logic from the view to the view model where it belongs and can be tested and evolved in isolation without the presence of a view.

Note that there are MVVM frameworks out there, such as for example Prism and MvvmLight, that provide implementations for ICommand and other MVVM related stuff to make your life easier.

thank you!!!! this works, this is the solution i used. thanks so much! — Tim, Oct 14 '19 at 02:10

score 0 · Answer 2 · answered Oct 11 '19 at 10:07

The intent of MVVM is to avoid the code behind and to separate view from the logic. use the commands in the viewModel and bind the view to those commands in the view. Viewmodel intern access the Model. something like below where ChartClickCommand should be implemented in ViewModel

<DataGrid x:Name="GridData" ItemsSource="{Binding MarketPriceGrid}">
  <DataGrid.ContextMenu>
    <ContextMenu>
      <MenuItem Header="OHLC Chart" Command={Binding ChartClickCommand}/>
     </ContextMenu>
    </DataGrid.ContextMenu>
</DataGrid>

WPF MVVM Can i use model from view

2 Answers2