c# - Simple WPF combobox filter

Question

I have searched Google for a simple solution to this but no luck. I have a standard WPF combo box which I would simply like to be able to filter the list displayed according to the first 2 or 3 letters a users types when the combo box has focus. I tried some coding including some lamba expressions but the error "System.NotSupportedException" keeps getting thrown on the line where "combobox.Items.Filter" is specified. I'm not using MVVM and would just like this simple functionality available for the user. Please help! P.S. IsEditable, IsTextSearchEnabled and StaysOpenOnEdit properties are set to true but the desired functionality is not yet achieved.

Answer 1

I have developed a sample application. I have used string as record item, you can do it using your own entity. Backspace also works properly.

 public class FilterViewModel
    {
        public IEnumerable<string> DataSource { get; set; }       

        public FilterViewModel()
        {
            DataSource = new[] { "india", "usa", "uk", "indonesia" };           
        }
    }

public partial class WinFilter : Window
    {
          public WinFilter()
          {
             InitializeComponent();

             FilterViewModel vm = new FilterViewModel();
             this.DataContext = vm;
          }

          private void Cmb_KeyUp(object sender, KeyEventArgs e)
          {
              CollectionView itemsViewOriginal = (CollectionView)CollectionViewSource.GetDefaultView(Cmb.ItemsSource);

              itemsViewOriginal.Filter = ((o) =>
              {
                  if (String.IsNullOrEmpty(Cmb.Text)) return true;
                  else
                  {
                     if (((string)o).Contains(Cmb.Text)) return true;
                     else return false;
                  }
              });

             itemsViewOriginal.Refresh();

             // if datasource is a DataView, then apply RowFilter as below and replace above logic with below one
             /* 
              DataView view = (DataView) Cmb.ItemsSource; 
              view.RowFilter = ("Name like '*" + Cmb.Text + "*'"); 
             */
          }
     }

XAML

<ComboBox x:Name="Cmb"
          IsTextSearchEnabled="False"
          IsEditable="True"
          ItemsSource="{Binding DataSource}"
          Width="120"
          IsDropDownOpen="True"
          StaysOpenOnEdit="True"
          KeyUp="Cmb_KeyUp" />