Combox not updating with binding

Question

Everytime i change my selected item inside my UI it's not updating my combobox.

XAML

<ComboBox x:Name="CompanyComboBox" HorizontalAlignment="Left" Height="26" 
    Margin="100,41,0,0" VerticalAlignment="Top" Width="144" 
    SelectionChanged="CompanyComboBox_SelectionChanged" 
    SelectedItem="{Binding SelectedCompany, UpdateSourceTrigger=PropertyChanged, Mode=OneWayToSource}">
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <ContentPresenter 
                Content="{Binding Converter={StaticResource DescriptionConverter}}">
            </ContentPresenter>
        </DataTemplate>
    </ComboBox.ItemTemplate>    
</ComboBox>

C#

private Company _selectedCompany;

public Company SelectedCompany
{
    get { return _selectedCompany; }
    set
    {
        if (value == _selectedCompany)
            return;
        _selectedCompany = value;
        OnPropertyChanged(nameof(SelectedCompany));
    }
}

Just to clarify the Company class is actually an ENUM

DescriptionConverter:

public class CompanyDescriptionConverter : IValueConverter
{
    public object Convert(object value, Type targetType, object parameter, CultureInfo culture)
    {
        var type = typeof(Company);
        var name = Enum.GetName(type, value);
        FieldInfo fi = type.GetField(name);
        var descriptionAttrib = (DescriptionAttribute)
            Attribute.GetCustomAttribute(fi, typeof(DescriptionAttribute));

        return descriptionAttrib.Description;
    }

    public object ConvertBack(object value, Type targetType, object parameter, CultureInfo culture)
    {
        throw new NotSupportedException();
    }
}

what i mean by inside my UI, is i have a list of companies set to a combobox item source, and when i change the combobox value to another company, it doesn't update in my source, it stay's as default.

My Enum might clarify the problem for someone:

 [Description("Netpoint Solutions")]
    Company1 = 0,

    [Description("Blackhall Engineering")]
    Company2 = 180,

What does your DescriptionConverter look like? Is it ever invoked? And what exactly do you mean by "change my selected item inside my UI" -- does that mean you select something in this particular combobox? Seeing more of your code would be helpful. — Petter Hesselberg, Sep 08 '17 at 11:45

score 2 · Accepted Answer · answered Sep 08 '17 at 13:01

Try to remove Mode=OneWayToSource and your event handler:

SelectionChanged="CompanyComboBox_SelectionChanged"

You don't need to handle the SelectionChanged event when you bind the SelectedItem property.

Also make sure that you set the DataContext to an instance of your class where the SelectedCompany property is defined.

Eike B · Answer 2 · 2017-09-08T11:37:39.977

0

Your Binding is defined as OneWayToSource. When you want it to be updated from the viewModel, you should set it to TwoWay.

See the documentation of Bindings for more details: https://msdn.microsoft.com/de-de/library/ms752347(v=vs.110).aspx

EDIT:

I skipped the part where you have an Enum as the source. I do not see, that you define the ItemsSource for the Combobox, where is this done? The value passed to the setter of SelectedCompany has to be in the Collection defined as ItemsSource.

For Enums, you can refer to this thread: How to bind an enum to a combobox control in WPF?

edited Sep 08 '17 at 11:37

answered Sep 08 '17 at 11:32

Eike B

231
1
7

i had it set to TwoWay aswell, still nothing happens when i change my selected item. – Corey James Carney Sep 08 '17 at 11:33
i define the itemsource like this CompanyComboBox.ItemsSource = Enum.GetValues(typeof(Company)).Cast(); – Corey James Carney Sep 08 '17 at 11:41
What exactly do you expect to happen? – mm8 Sep 08 '17 at 11:58
i expect it to be bound? so when i change my selected item from company1 to company 2, the SelectedCompany field should update to Company2 then i can use that throughout the clas. – Corey James Carney Sep 08 '17 at 12:07
Should work if the types match and you remove " Mode=OneWayToSource". Did you put a breakpoint in the setter of SelectedCompany? And what are you doing in CompanyComboBox_SelectionChanged? – mm8 Sep 08 '17 at 12:09
i have added a breakpoint inside the SelecCompanySetter, it doesn't get hit when my property changes. – Corey James Carney Sep 08 '17 at 12:29
What about your event handler? Try to remove it. And how do you set the DataContext? – mm8 Sep 08 '17 at 12:35

Combox not updating with binding

2 Answers2