How to Correctly Bind a WPF ComboBox to a Custom List and Resolve DataContext Issues?

WPF ComboBox Binding with Custom List: Understanding Binding Hierarchy

In WPF data binding, child elements within a DataTemplate inherit the DataContext of their parent element. This means that a ComboBox inside a DataTemplate will automatically have its DataContext set to the underlying ViewModel object represented by the DataTemplate.

Data binding issue

In the provided code example, the ComboBox does not update the SelectedItem/SelectedValue binding because the DataContext is not set correctly. This problem can be solved by explicitly setting the DataContext in the MainWindow's code-behind file.

public partial class Window1
{
    public Window1()
    {
        InitializeComponent();
        DataContext = new MainWindowViewModel();
    }
}

Correct binding configuration

After setting the DataContext, the binding configuration of the ComboBox should look like this:

<ComboBox ItemsSource="{Binding Path=PhonebookEntries}"
          DisplayMemberPath="Name"
          SelectedValuePath="Name"
          SelectedValue="{Binding Path=PhonebookEntry}" />

• ItemsSource: Specifies the collection of items to be displayed in the ComboBox.
• DisplayMemberPath: Specifies the properties of each item to be displayed in the list.
• SelectedValuePath: Specifies the properties of each item to be used as the value.
• SelectedValue: Specifies the ViewModel property representing the selected item.

Modification: Data binding issue using CollectionView

If using CollectionView for PhonebookEntries property, it is recommended to use a derived class. This is because using CollectionView directly leads to inefficiencies and potential errors. By using derived classes, you can implement advanced functionality while avoiding known issues.

Use ToString() in dropdown list content

To avoid potential binding issues, you can use ToString() instead of DisplayMemberPath to display the dropdown content. ToString() represents the string representation of each item, and DisplayMemberPath specifies the member used to select and display the item.

<ComboBox ItemsSource="{Binding Path=PhonebookEntries}"
          SelectedValuePath="Name"
          SelectedValue="{Binding Path=PhonebookEntry}" />

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