ComboBox中的SelectedItem绑定

Question

I have a problem with binding to SelectedItem property of ComboBox.

There is an ObservableCollection, which is binded to ItemsSource property and another object field, which I want to bind to SelectedItem property, in the app.

But the application doesn't even start, because of Target Invocation Exception.

I don't know, if is it important to bind SelectedItem with one of the property of one instance of ItemsSource or I can use declare another property in viewmodel for it. I tried both variants. Didn't help. I've read some threads about such problem, but those solutions doesn't solve this.

<ComboBox x:Name="CategoryComboBox"
                  ItemsSource="{Binding CategoryList}"
                  DisplayMemberPath="Name"
                  SelectedItem="{Binding SelectedCategory, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"
                  SelectionChanged="CategoryComboBox_SelectionChanged"
                  />



public ObservableCollection<IItem> CategoryList { get; set; }

public IItem SelectedCategory
{
    get
    {
        return _selectedCategory;
    }
    set
    {
        _selectedCategory = value;
        RaisePropertyChangedEvent(nameof(SelectedCategory));
    }
}

public interface IItem
{
    int Id { get; set; }
    string Name { get; set; }
}

private void CategoryComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
{         
    var catName = (e.AddedItems[0] as IItem).Name;
    vm.SelectedCategory = vm.CategoryList.Where(w => w.Name == catName).Select(s => s.Id).FirstOrDefault();
}

    public void LoadLanguageList()
    {            
        LanguageList = Repository.Current.GetLanguageList();
        _selectedLanguage = LanguageList.FirstOrDefault(i => i.Id == 1);
        RaisePropertyChangedEvent(nameof(SelectedLanguage));
    }

In the code upper you can see the way, how I try to bind, then the collection property, selected item property and the type of items as interface.

I know, that it's impossible to create an instance of interface, but I don't know if binding object of such type is incorrect. But I tried to bind to another object type of class, which implements this interface, and the result was the same.

Answer 1

SelectedCategory= CategoryList [0];

vm.SelectedCategory = vm.CategoryList.Where(w => w.Name == catName).FirstOrDefault();

these 2 need to be changed

Note: you don't have to create an event for SelectionChanged . if the item is changed in ui it will automatically assign to SelectedCategory im assuming ur using MVVM so u set data context