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Validate user action when removing items from RadAutoCompleteBox


Product Version Product Author
2021.1.223 RadAutoCompleteBox for WinForms Nadya Karaivanova


A common requirement is to validate the user action when he/she wants to remove a tokenized item from the text box field in RadAutoCompleteBox. This article will demonstrate how you can achieve this by displaying a message box which ensures whether the item should be removed or not.



This can be achieved with using a custom text block element. First, it is necessary to create a custom class that inherits from the TokenizedTextBlockElement class. Then, override the OnRemoveButtonClick method where the actual removing of items is happening:

public class MyTokenizedTextBlockElement : TokenizedTextBlockElement
    protected override void CreateChildElements()


    protected override void OnRemoveButtonClick()
        if (RadMessageBox.Show("Are you sure you want to delete item: " + this.Item.Text, "Action needed",
            MessageBoxButtons.YesNo) == System.Windows.Forms.DialogResult.Yes)
    protected override Type ThemeEffectiveType
            return typeof(TokenizedTextBlockElement);

Public Class MyTokenizedTextBlockElement
    Inherits TokenizedTextBlockElement
    Protected Overrides Sub CreateChildElements()
    End Sub
    Protected Overrides Sub OnRemoveButtonClick()
        If RadMessageBox.Show("Are you sure you want to delete item: " & Me.Item.Text, "Action needed", MessageBoxButtons.YesNo) = System.Windows.Forms.DialogResult.Yes Then
        End If
    End Sub
    Protected Overrides ReadOnly Property ThemeEffectiveType As Type
            Return GetType(TokenizedTextBlockElement)
        End Get
    End Property
End Class

Then, you should replace the default item with the newly created custom one in the CreateTextBlock event:

public RadForm1()

    List<Country> items = new List<Country>();
    items.Add(new Country(1, "Germany"));
    items.Add(new Country(2, "USA"));
    items.Add(new Country(3, "Brazil"));
    items.Add(new Country(4, "Bulgaria"));
    items.Add(new Country(5, "Greece"));
    this.radAutoCompleteBox1.AutoCompleteDataSource = items;
    this.radAutoCompleteBox1.AutoCompleteDisplayMember = "Name";
    this.radAutoCompleteBox1.AutoCompleteValueMember = "Id";
    this.radAutoCompleteBox1.ShowRemoveButton = true;
    this.radAutoCompleteBox1.CreateTextBlock += this.RadAutoCompleteBox1_CreateTextBlock;

private void RadAutoCompleteBox1_CreateTextBlock(object sender, CreateTextBlockEventArgs e)
    TokenizedTextBlockElement element = e.TextBlock as TokenizedTextBlockElement;
    if (element != null)
        e.TextBlock = new MyTokenizedTextBlockElement();

public class Country
    public int Id { get; set; }

    public string Name { get; set; }

    public Country(int id, string name)
        this.Id = id;
        this.Name = name;

Public Sub New()
    Dim items As List(Of Country) = New List(Of Country)()
    items.Add(New Country(1, "Germany"))
    items.Add(New Country(2, "USA"))
    items.Add(New Country(3, "Brazil"))
    items.Add(New Country(4, "Bulgaria"))
    items.Add(New Country(5, "Greece"))
    Me.RadAutoCompleteBox1.AutoCompleteDataSource = items
    Me.RadAutoCompleteBox1.AutoCompleteDisplayMember = "Name"
    Me.RadAutoCompleteBox1.AutoCompleteValueMember = "Id"
    Me.RadAutoCompleteBox1.ShowRemoveButton = True
    AddHandler Me.RadAutoCompleteBox1.CreateTextBlock, AddressOf Me.RadAutoCompleteBox1_CreateTextBlock
End Sub

Private Sub RadAutoCompleteBox1_CreateTextBlock(ByVal sender As Object, ByVal e As CreateTextBlockEventArgs)
    Dim element As TokenizedTextBlockElement = TryCast(e.TextBlock, TokenizedTextBlockElement)

    If element IsNot Nothing Then
        e.TextBlock = New MyTokenizedTextBlockElement()
    End If
End Sub

Public Class Country
    Public Property Id As Integer
    Public Property Name As String

    Public Sub New(ByVal id As Integer, ByVal name As String)
        Me.Id = id
        Me.Name = name
    End Sub
End Class

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