Bind ComboBox to custom list in WPF

WPF's ComboBox control provides flexible data binding options, including the ability to display and select values ​​from a custom object list. This guide explores how to bind ComboBox to a custom list in WPF and solves common problems.

Bind to custom list

To bind a ComboBox to a custom list, you need a class that represents the list data structure. For example, if you have a list of phonebook entries, you can define a PhoneBookEntry class that contains properties such as name and number.

Next, create a ConnectionViewModel that exposes a collection of PhoneBookEntry objects. This view model will act as a data source for ComboBox.

In your XAML, bind the ItemsSource property of ComboBox to the PhonebookEntries property of the view model. Additionally, set the DisplayMemberPath property to specify which property should be displayed in the drop-down list, and the SelectedValuePath property to indicate which property should be used when selecting an item to set the SelectedValue property.

Data flow and binding direction

Binding is bidirectional by default, allowing changes made in the UI or view model to propagate to both sides. However, in some cases, you may want to specify a one-way binding, for example, when you just want to update the view model when changes occur in the UI.

Ensure the correct context

ComboBox's DataContext should be a ConnectionViewModel instance that provides a custom list. If the DataContext is not explicitly set, WPF will try to infer it based on surrounding elements and binding hierarchy.

Understand the implicit inheritance of DataContext

When adding items to ComboBox through ItemsControl or ItemsPanel, they inherit the DataContext of the parent element by default. This means that the DataContext of each item in the ComboBox within the ItemsControl is the same as the DataContext of its ItemsControl itself.

Solve CollectionView Problem

If the PhonebookEntries property on the ConnectionViewModel is a CollectionView, you may encounter two-way binding issues. To resolve this, consider changing the property type to ReadOnlyCollection or implementing a custom ICollectionView derived class.

Alternative Method for DisplayMemberPath

In some cases, you may prefer to use the ToString() method of a custom class instead of DisplayMemberPath. This allows for greater control over the text displayed in the drop-down list, while still using the SelectedValue property to store the selected value.