WPF - MVVM - ComboBox SelectedItem

Question

I have ViewModel(implemented INotifyPropertyChanged) in the background and class Category which has only one property of type string

Answer 1

The category you are setting in this line -

NodeCategory = some_list_of_other_objects.Category;

and one present in your Categories collection(ItemsSource="{Binding Categories}") should be referring to same object. If they are not then SelectedItem won't work.

Solution 1 -

You can also try to use SelectedValuePath like this -

and in code you can do something like this -

private string _NodeCategory;
public string NodeCategory
{
    get
    {
        return _NodeCategory;
    }
    set
    {
        _NodeCategory = value;
        OnPropertyChanged("NodeCategory");
    }
}

and set selected item like this -

NodeCategory = some_list_of_other_objects.Category.Name;

and use selected value like this -

Category selectedCategory = 
   some_list_of_other_objects.FirstOrDefault(cat=> cat.Name == NodeCategory);

or

Category selectedCategory = 
   Categories.FirstOrDefault(cat=> cat.Name == NodeCategory);

---

Solution 2 -

Another possible solution can be -

NodeCategory = 
  Categories.FirstOrDefault(cat=> cat.Name == some_list_of_other_objects.Category.Name);

this way your NodeCategory property will have the reference of an object in Categories collection and SelectedItem will work.