How to Bind a WPF ComboBox to a Custom List?

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 a ComboBox to a custom list in WPF and solves common problems.

Bind to custom list

To bind a ComboBox to a custom list, a class representing the list data structure is required. For example, if you have a list of phone book 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 the data source for the ComboBox.

In your XAML, bind the ComboBox's ItemsSource property to the view model's PhonebookEntries property. 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

By default, bindings are bidirectional, allowing changes made in the UI or view model to propagate to both parties. However, there are situations where you may want to specify one-way binding, for example when you only want to update the view model when a change occurs in the UI.

Ensure correct context

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

Understanding the implicit inheritance of DataContext

When items are added to a ComboBox via ItemsControl or ItemsPanel, they inherit the parent element's DataContext by default. This means that the DataContext of each item in the ComboBox within the ItemsControl is the same as the DataContext of the ItemsControl itself.

Solving CollectionView issues

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

Alternatives to DisplayMemberPath

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

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