//File:Window.xaml.vb Imports System.Windows Imports System.Windows.Documents Imports System.Windows.Input Namespace WpfApplication1 Public Partial Class Window1 Inherits Window Public Sub New() InitializeComponent() End Sub Private Sub btnInsert_Click(sender As Object, e As RoutedEventArgs) If String.IsNullOrEmpty(tbxInsertionText.Text) Then Return End If rtbTextContent.BeginChange() If rtbTextContent.Selection.Text <> String.Empty Then rtbTextContent.Selection.Text = String.Empty End If Dim tp As TextPointer = rtbTextContent.CaretPosition.GetPositionAtOffset(0, LogicalDirection.Forward) rtbTextContent.CaretPosition.InsertTextInRun(tbxInsertionText.Text) rtbTextContent.CaretPosition = tp rtbTextContent.EndChange() Keyboard.Focus(rtbTextContent) End Sub End Class End Namespace