Creating Custom Blocks

RadAutoCompleteBox allows not only appearance customization via the formatting event, but also replacement of the default UI block representation. The CreateTextBlock event exposes this possibility.

You should create a custom text block that inherits from ITextBlock and any inheritor of RadElement. Let’s extend the default TokenizedTextBlockElement by adding a check box. You don’t need to implement the ITextBlock interface, because it is already defined in the base class:

• C#
• VB.NET

public class MyTokenizedTextBlockElement : TokenizedTextBlockElement
{
    private RadCheckBoxElement checkBox;
    protected override Type ThemeEffectiveType
    {
        get
        {
            return typeof(TokenizedTextBlockElement);
        }
    }
    protected override void CreateChildElements()
    {
        base.CreateChildElements();
        int index = this.Children.IndexOf(this.RemoveButton);
        this.checkBox = new RadCheckBoxElement();
        this.checkBox.StretchVertically = true;
        this.checkBox.StretchHorizontally = false;
        this.Children.Insert(index, this.checkBox);
    }
}

Public Class MyTokenizedTextBlockElement
    Inherits TokenizedTextBlockElement
    Private checkBox As RadCheckBoxElement
    Protected Overrides ReadOnly Property ThemeEffectiveType() As Type
        Get
            Return GetType(TokenizedTextBlockElement)
        End Get
    End Property
    Protected Overrides Sub CreateChildElements()
        MyBase.CreateChildElements()
        Dim index As Integer = Me.Children.IndexOf(Me.RemoveButton)
        Me.checkBox = New RadCheckBoxElement()
        Me.checkBox.StretchVertically = True
        Me.checkBox.StretchHorizontally = False
        Me.Children.Insert(index, Me.checkBox)
    End Sub
End Class

Then you should replace the default text block in the CreateTextBlock event handler, in the following manner:

• C#
• VB.NET

private void radAutoCompleteBox1_CreateTextBlock(object sender, CreateTextBlockEventArgs e)
{
    if (e.TextBlock is TokenizedTextBlockElement)
    {
        e.TextBlock = new MyTokenizedTextBlockElement();
    }
}

Private Sub radAutoCompleteBox1_CreateTextBlock(sender As Object, e As CreateTextBlockEventArgs)
    If TypeOf e.TextBlock Is TokenizedTextBlockElement Then
        e.TextBlock = New MyTokenizedTextBlockElement()
    End If
End Sub

Finally, the text property should be set:

The subscription to the event, should be introduced before setting the text of the control.

• C#
• VB.NET

radAutoCompleteBox1.CreateTextBlock+=new CreateTextBlockEventHandler(radAutoCompleteBox1_CreateTextBlock);
this.radAutoCompleteBox1.Text = "Euro;USD;GBP;";

AddHandler RadAutoCompleteBox1.CreateTextBlock, AddressOf radAutoCompleteBox1_CreateTextBlock
Me.RadAutoCompleteBox1.Text = "Euro;USD;GBP;"

The following image demonstrates the final result: