如何将基于键的字典值绑定到Code-Behind中的TextBlock？

Question

I am using the MVVM model with a dynamic field generator, where the field is pulled from the database, done this way because different types of forms require different fields (TextBox/TextBlock, ComboBox, etc.). The problem is I'm trying to retrieve a value from a dictionary, to display in a TextBlock for the form, but I'm not sure how to bind the retrieved Key so I can display the value.

Currently, I am doing the following:

 TextBlock textBlock = new TextBlock();
 textBlock.SetBinding(TextBlock.TextProperty, createFieldBinding(myPropertyName);

With the following binding method:

 private Binding createFieldBinding(string fieldName) {
      Binding binding = new Binding(fieldName);
      binding.Source = this.DataContext;
      binding.UpdateSourceTrigger = UpdateSourceTrigger.LostFocus;
      return binding;
 }

Where I pass something through like Score , which maps to a Score property in the ViewModel, but how would I bind to a Dictionary Key to retrieve its Value?

I want to be able to bind to something like myDictionaryProperty[myDictionaryKey] , if that is possible.

Example: The below generates the PlayerScore for Player with ID of 1. Where PlayerScore is a Dictionary<int, int> and PlayerID is an int .

 <TextBlock Name="textBlockA" Text="{Binding PlayerScore[1]} />

Answer 1

Binding to indexed properties is possible and uses the same notation as C#, just like you wrote:

<TextBlock Name="textBlockA" Text="{Binding PlayerScore[1]}" />

The string you pass to "createFieldBinding" is the property path. If you set the source as the dictionary, you just need to pass the indexer part, like "[ 1 ]", as if you had done like this in xaml:

<TextBlock Name="textBlockA" Text="{Binding [1]}" />

See this

Answer 2

Using this solution provided by @Clemens, I was able to build my own DictionaryItemConverter, based on the data types for my Dictionary, and create a multi-binding method that would bind the Key and the Dictionary together.

Converter:

 public class DictionaryItemConverter : IMultiValueConverter {
      public object Convert(object[] values, Type targetType, object parameter, System.Globalization.CultureInfo culture) {
           if(values != null && values.Length >= 2) {
                var myDict = values[0] as IDictionary;
                if(values[1] is string) {
                     var myKey = values[1] as string;
                     if(myDict != null && myKey != null) {
                          //the automatic conversion from Uri to string doesn't work
                          //return myDict[myKey];
                          return myDict[myKey].ToString();
                     }
                }
                else {
                     long? myKey = values[1] as long?;
                     if(myDict != null && myKey != null) {
                          //the automatic conversion from Uri to string doesn't work
                          //return myDict[myKey];
                          return myDict[myKey].ToString();
                     }
                }
           }

           return Binding.DoNothing;
      }

      public object[] ConvertBack(object value, Type[] targetTypes, object parameter, System.Globalization.CultureInfo culture) {
           throw new NotSupportedException();
      }
 }

Multi-Bind Method:

 private MultiBinding createFieldMultiBinding(string fieldName) {
      // Create the multi-binding
      MultiBinding mbBinding = new MultiBinding();
      // Create the dictionary binding
      Binding bDictionary = new Binding(fieldName + "List");
      bDictionary.Source = this.DataContext;
      // Create the key binding
      Binding bKey = new Binding(fieldName);
      bKey.Source = this.DataContext;
      // Set the multi-binding converter
      mbBinding.Converter = new DictionaryItemConverter();
      // Add the bindings to the multi-binding
      mbBinding.Bindings.Add(bDictionary);
      mbBinding.Bindings.Add(bKey);

      return mbBinding;
 }