Imports Telerik.WinControls.UI

Public Class RadForm1
    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        Dim str As String = "Item 1;Item 2;Item 3;Item 4;Item 5;Item 6;Item 7;Item 8;Item 9;Item 10;"
        RadAutoCompleteBox1.Multiline = True
        RadAutoCompleteBox1.Text = str

    End Sub

    Private Sub RadAutoCompleteBox1_SelectionChanged(sender As Object, e As SelectionChangedEventArgs) Handles RadAutoCompleteBox1.SelectionChanged
        Dim SelectedItem As String = RadAutoCompleteBox1.Text.Substring(e.SelectionStart, e.SelectionLength)
        Debug.Print(SelectedItem)
    End Sub
End Class