WPF binding tricky issue - wpf

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>

Answer 2

First of all, I suppose you should use #Jay's approach and make ChosenFeatures Dictionary also.
However you can use Converter instead and pass your dictionary like a parameter while binding:
public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
{
var key = (string)value;
var dictionary = (Dictionary<string, double>)parameter;
if (dictionary.ContainsKey(key))
return dictionary[key];
else
return null;
}

Answer 3

Instead of binding "ChosenFeatures" bind "AllFeatureCosts". We know that it will display complete list and we can then write a simple Multibinding visibility converter to display the items which are selected (in ChosenFeatures).
Note:
Depending on the size of the dictionary it may affect application performance...