在选定的indexchange事件触发后填充控件

Question

I have a MVVM WPF project where I have an devexpress accordian control which is populated with xml template items from a ViewModel. That works great, but my problem is when I click on one of the items in the accordian control and the selectedIndexChanged event is fired. I want to handle that in the MVVM manner and get the selected items value(which is a path to an xml file) from the accordian control, fetch the content of the xml file and databind a textbox control with the content of the xml file. The following is what I have tried so far.

Here is my xaml user control

<dxa:AccordionControl Grid.Column="0" x:Name="accordianTemplateMenu" 
SelectionMode="Single" SelectionUnit="SubItemOrRootItem" ItemsSource="
{Binding TemplateItems}"
  ChildrenPath="TemplateItems" DisplayMemberPath="Header >
    <dxmvvm:Interaction.Behaviors>
        <dxmvvm:EventToCommand EventName="SelectedItemChanged" Command="
{Binding EditCommand}">
            <dxmvvm:EventToCommand.EventArgsConverter>
                <Common:AccordionEventArgsConverter/>
            </dxmvvm:EventToCommand.EventArgsConverter>
        </dxmvvm:EventToCommand>
    </dxmvvm:Interaction.Behaviors>
</dxa:AccordionControl>

<GridSplitter Grid.Column="1" />

<TextBlock Grid.Column="2" x:Name="templateItemContainer">
    <Run Name="run" Text="{Binding XML}" ></Run>
</TextBlock>

This boils down to the AccordionEventArgsConverter which gets me the event arguments from the selecteditem in the accordian control:

public class AccordionEventArgsConverter : 
EventArgsConverterBase<AccordionSelectedItemChangedEventArgs>
{
    protected override object Convert(object sender, 
AccordionSelectedItemChangedEventArgs args)
    {
        if (args != null)
        {
            return args;
        }
        return null;
    }
}

And finally my viewmodel:

class TemplateMenuViewModel
{
    private List<TemplateItem> _templateItems;

    public TemplateMenuViewModel()
    {
        EditCommand = new DelegateCommand<object>(Edit, CanEdit);
    }

    public List<TemplateItem> TemplateItems
    {
        get
        {
            TemplateProvider provider = new TemplateProvider();
            return provider.GetTemplateMenuItems("pathToMenuItems");
        }
        set { _templateItems = value; }
    }

    public ICommand<object> EditCommand { get; private set; }

    public void Edit(object accordianItemArgs)
    {

    }

    public bool CanEdit(object accordianItemArgs)
    {
        return accordianItemArgs != null;
    }
}

I am able to get into the public void Edit method, which is great because from there I can use the accordianItemArgs to get the xml content, but how do I "return"/databind the xml content to the textblock element in the xaml file?

Answer 1

There are a couple of things:

• You need the TemplateMenuViewModel to define an XML property. It looks like your TextBlock is already binding to it.
• Then you need your ViewModel to implement the INotifyPropertyChanged interface. It doesn't look like you're doing that, then raise a property changed event when the XML text is set.

• You should set your Text="{Binding XML}" with a Mode of OneWay:

  Text="{Binding XML, Mode=OneWay}"

If you need more information on how to implement INotifyPropertyChanged , check out this tutorial: https://www.tutorialspoint.com/mvvm/mvvm_first_application.htm .