WPF binding textbox to dictionary entry

There is a Binding error in your code because MyDict is not a property. You have to bind to a Property and not to a Field

System.Windows.Data Error: 40 : BindingExpression path error: 'MyDict' property not found on 'object' ''MainWindow' (Name='')'. BindingExpression:Path=MyDict[First]; DataItem='MainWindow' (Name=''); target element is 'TextBox' (Name='textBox1'); target property is 'Text' (type 'String')

Change the MyDict Field to a Property like shown below

    private Dictionary<string, string> _MyDict;    public Dictionary<string, string> MyDict    {        get { return _MyDict; }        set { _MyDict = value; }    }

In the constructor of your ViewModel initialize MyDict.

        MyDict = new Dictionary<string, string>        {            {"First", "Test1"},            {"Second", "Test2"}        };

The following two variants will not work as MyDict["key"] returns a string and string does not have a Text or Value property. The other two variants should work.

Text="{Binding MyDict[First].Text}"Text="{Binding MyDict[First].Value}"

The following bindings will work

Text="{Binding MyDict[First]}"Text="{Binding Path=MyDict[First]}"