Creating custom blocks

Updated over 6 months ago

The RadTextBoxControl allows not only appearance customizations via the formatting event, but also a 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 create a button text block that should be created for each occurrence of the string here:

First, you should create a button that implements ITextBlock interface:

C#

        
public class ButtonTextBlock : RadButtonElement, ITextBlock
{
    private int index;
    private int offset;
    public ButtonTextBlock()
    {
        this.index = 0;
        this.offset = 0;
        this.MaxSize = new Size(0, 12);
    }
        
    protected override Type ThemeEffectiveType
    {
        get
        {
            return typeof(RadButtonElement);
        }
    }
        
    public int Index
    {
        get
        {
            return this.index;
        }
        set
        {
            this.index = value;
        }
    }
        
    public int Length
    {
        get
        {
            return 1;
        }
    }
        
    public int Offset
    {
        get
        {
            return this.offset;
        }
        set
        {
            this.offset = value;
        }
    }
            
    public int GetCharacterIndexFromX(float x)
    {
        RectangleF bounds = this.ControlBoundingRectangle;
        float median = bounds.X + bounds.Width / 2;
        return x <= median ? 0 : 1;
    }
    
    public RectangleF GetRectangleFromCharacterIndex(int index, bool trailEdge)
    {
        Rectangle bounds = this.ControlBoundingRectangle;
        
        if (index == 1)
        {
            bounds.X = bounds.Right;
            bounds.Width = 0;
        }
    
        return bounds;
    }
        
    protected override void OnClick(EventArgs e)
    {
        base.OnClick(e);
        RadMessageBox.Show("The button is clicked.", "Message");
    }
}

VB.NET

    
Public Class ButtonTextBlock
Inherits RadButtonElement
Implements ITextBlock
    Private m_index As Integer
    Private m_offset As Integer
    Public Sub New()
        Me.m_index = 0
        Me.m_offset = 0
        Me.MaxSize = New Size(0, 12)
    End Sub
    Protected Overrides ReadOnly Property ThemeEffectiveType() As Type
        Get
            Return GetType(RadButtonElement)
        End Get
    End Property
    Public Property Index() As Integer Implements ITextBlock.Index
        Get
            Return Me.m_index
        End Get
        Set(value As Integer)
            Me.m_index = value
        End Set
    End Property
    Public ReadOnly Property Length() As Integer Implements ITextBlock.Length
        Get
            Return 1
        End Get
    End Property
    Public Property Offset() As Integer Implements ITextBlock.Offset
        Get
            Return Me.m_offset
        End Get
        Set(value As Integer)
            Me.m_offset = value
        End Set
    End Property
    Public Function GetCharacterIndexFromX(x As Single) As Integer Implements ITextBlock.GetCharacterIndexFromX
        Dim bounds As RectangleF = Me.ControlBoundingRectangle
        Dim median As Single = bounds.X + bounds.Width / 2
        Return If(x <= median, 0, 1)
    End Function
    Public Function GetRectangleFromCharacterIndex(index As Integer, trailEdge As Boolean) As RectangleF Implements ITextBlock.GetRectangleFromCharacterIndex
        Dim bounds As Rectangle = Me.ControlBoundingRectangle
        If index = 1 Then
            bounds.X = bounds.Right
            bounds.Width = 0
        End If
        
        Return bounds
    End Function
    Protected Overrides Sub OnClick(e As EventArgs)
        MyBase.OnClick(e)
        RadMessageBox.Show("The button is clicked.", "Message")
    End Sub
    Overloads Sub Measure(availableSize As SizeF) Implements ITextBlock.Measure
        MyBase.Measure(availableSize)
    End Sub
    Overloads Sub Arrange(finalRectangle As RectangleF) Implements ITextBlock.Arrange
        MyBase.Arrange(finalRectangle)
    End Sub
    Overloads ReadOnly Property DesiredSize As SizeF Implements ITextBlock.DesiredSize
        Get
            Return MyBase.DesiredSize
        End Get
    End Property
    Overloads ReadOnly Property ControlBoundingRectangle As Rectangle Implements ITextBlock.ControlBoundingRectangle
        Get
            Return MyBase.ControlBoundingRectangle
        End Get
    End Property
    Overloads Property Text As String Implements ITextBlock.Text
        Get
            Return MyBase.Text
        End Get
        Set(value As String)
            MyBase.Text = value
        End Set
    End Property
End Class

Then you should subscribe to the CreateTextBlock event before initializing the Text property:

C#

        
radTextBoxControl1.CreateTextBlock += new CreateTextBlockEventHandler(radTextBoxControl1_CreateTextBlock);

VB.NET

AddHandler RadTextBoxControl1.CreateTextBlock, AddressOf radTextBoxControl1_CreateTextBlock

C#

void radTextBoxControl1_CreateTextBlock(object sender, CreateTextBlockEventArgs e)
{
    if (e.Text == "here")
    {
        e.TextBlock = new ButtonTextBlock();
    }
}

VB.NET

Private Sub radTextBoxControl1_CreateTextBlock(sender As Object, e As CreateTextBlockEventArgs)
    If e.Text = "here" Then
        e.TextBlock = New ButtonTextBlock()
    End If
End Sub

Finally, the Text property should be set:

C#

this.radTextBoxControl1.Text = "Please, click here";

VB.NET

Me.RadTextBoxControl1.Text = "Please, click here"

Figure 1: The "here" word is replaced with a button.

See Also

• Caret positioning and selection
• AutoComplete
• Structure
• Properties and Events
• Text editing