Signum Documentation

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AutoCompleteTextBox is a TextBox with a ListBox in a Popup that appears when you write text, filling the list from an external source of possible values.

By double-clicking on an element in the Pop-up (or pressing Enter) the element becomes the SelecteItem.


public partial class AutoCompleteTextBox : UserControl
   public object SelectedItem;
   public bool AllowFreeText;

   public int MinTypedCharacters;
   public TimeSpan Delay;

   public DataTemplate ItemTemplate;
   public DataTemplateSelector ItemTemplateSelector; 
  • SelectedItem: The item that the user selected the last time the pop-up was opened, or the text that is written if AllowFreeText == true, otherwise false.
  • AllowFreeText: Controls if the written string or null should be placed in SelectedItem if no matching element was found. Default is false.
  • MinTypedCharacters: Controls the minimum number of character to start requesting elements using Autocompleting. Default 1.
  • Delay: Minimum amount of time after the last keystroke, in milliseconds, to start requesting elements using Autocompleting. Default 300 ms.
  • ItemTemplate: The ItemTemplate that will be used in the ListBox inside the Popup.
  • ItemTemplateSelector: The ItemTemplateSelector that will be used in the ListBox inside the Popup.


public partial class AutoCompleteTextBox : UserControl
   public event ClosedEventHandler Closed;
   public event Func<string, CancellationToken, IEnumerable> Autocompleting;

public class CloseEventArgs : RoutedEventArgs
    public CloseReason Reason { get; }
    public bool IsCommit { get; }

public enum CloseReason

The most important even is the mandatory Autocompleting that is called in a background thred and provides the string term to look for and a CancellationToken that can be used to cancel any pending request that won't be necessary.

Additionally, Closed events gives detailed information of the reason the popup was Closed and if this action commited a change in the SelectedItem or not.


    Autocompleting="AutoCompleteTextBox_AutoCompleting" />
private IEnumerable AutoCompleteTextBox_AutoCompleting(string arg, CancellationToken token)
    if (string.IsNullOrEmpty(arg))
        return null;

    string dir = System.IO.Path.GetDirectoryName(arg);

    if (string.IsNullOrEmpty(dir))
        return null;

    string file = System.IO.Path.GetFileName(arg);
    DirectoryInfo di = new DirectoryInfo(dir);

    var directories = di.GetDirectories(file + "*").Select(a => a.FullName);
    var files = di.GetFiles(file + "*.*").Select(a => a.FullName);

    return directories.Concat(files).ToArray();