Question

I need some assistance to implement some data binding. My viewmodel exposes the following properties:

public List<string> ChosenFeatures {get;set;}
public Dictionary<string, double> AllFeatureCosts {get;set;}

“ChosenFeatures” will contain a subset of dictionary keys present in “AllFeatureCosts”.

In the view I would like to render a series of TextBlocks, one for each item in “ChosenFeatures”. Here’s the tricky part:- the Text property of each TextBlock need to be bound to a value in the “AllFeatureCosts” dictionary, using the string in “ChosenFeatures” as the key to that dictionary item.

I would be grateful for any pointers on how to write the XAML to accomplish this.

Answer 1

Provide a ViewModel for the data, thats the reason to use MVVM in the first place.

class FeatureViewModel
{
    public FeatureViewModel(MyViewModel aViewModel, string aKey)
    {
        mParent = aViewModel;
        mKey = aKey
    }
    public string Value
    {
        get{return mParent.AllFeatureCosts[mKey];}
    }
}

add a collection for your viewmodels to your main viewmodel

public ObservableCollection<FeatureViewModel> Features{ get; set; }

and initialize it somewhere

foreach(var feature in ChosenFeatures)
{
    Features.Add(new VisualFeature(this, feature) );
}

from here you can also if necessary and if you have INotifyPropertyChanged properly implemented, raise any changes on the FeatureViewModels. You of course need to keep these collections in sync, which might be a bit of work.

Of course, your DataTemplate needs some adjustments aswell

<DataTemplate DataType="{x:Type FeatureViewModel}">
    <TextBlock Text="{Binding Value}"/>
</DataTemplate>