WPF ComboBox initial state from a string property

Question

I have a simple combo :

     <ComboBox x:Name="testCombo" SelectedValue="{Binding State, Mode=TwoWay}" VerticalAlignment="Center" HorizontalAlignment="Center" MinWidth="100">
        <ComboBoxItem>OPEN</ComboBoxItem>
        <ComboBoxItem>CLOSED</ComboBoxItem>
    </ComboBox>

That state is just a string property with INotifyPropertyChanged implemented.

    private string state;

    public string State
    {
        get { return state; }
        set
        {
            state = value;
            OnPropertyChanged("State");
        }
    }

What i want to achieve is, when that State string property is initially set to "OPEN", when my window loads, the ComboBox to set it's initial item as "OPEN".

I also tried to attach a converter there:

    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        ComboBoxItem cbi = new ComboBoxItem();

        cbi.Content = value as string;

        return cbi;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        return (value as ComboBoxItem).Content;
    }

With this, my State string property will be fine populated, but the ComboBox won't get to the desired initial state.

Open and closed? Converters? is this a bit complex. Can you boil your problem down to: [Bind Combobox to a boolean](http://stackoverflow.com/questions/4335339/how-to-bind-a-boolean-to-combobox-in-wpf)? — Nathan Cooper, Jan 22 '15 at 15:57

score 2 · Accepted Answer · answered Jan 22 '15 at 15:58

ComboBoxItem is not compared by content but by reference and the instance you create in converter is not the same instance displayed in ComboBox so they will never be equal. What you can do is set ItemsSource as list of strings and bind SelectedItem directly to string property without any converter

<ComboBox SelectedItem="{Binding State, Mode=TwoWay}" x:Name="testCombo">
    <ComboBox.ItemsSource>
        <x:Array Type="{x:Type sys:String}">
            <sys:String>OPEN</sys:String>
            <sys:String>CLOSED</sys:String>
        </x:Array>
    </ComboBox.ItemsSource>
</ComboBox>

you'll need to add sys namespace to your XAML as well

xmlns:sys="clr-namespace:System;assembly=mscorlib"

WPF ComboBox initial state from a string property

1 Answers1