Public Class Form1
    Private _Datasource As New List(Of String)

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        For index = 1 To 1000000
            _Datasource.Add($"item-{index}")
        Next

        Dim oDatatable = GetDatatable(10)
        Dim oSelectedValues = _Datasource.Take(1).ToList()

        LookupControl.DataSource = oDatatable
        LookupControl.SelectedValues = oSelectedValues
        LookupControl.ReadOnly = False

        LookupControl21.DataSource = oDatatable
        LookupControl21.SelectedValues = oSelectedValues
        LookupControl21.ReadOnly = True

        LookupControl22.DataSource = oDatatable
        LookupControl22.SelectedValues = oSelectedValues
        LookupControl22.ReadOnly = False
        LookupControl22.MultiSelect = False

        LookupControl22.SelectedValues = New List(Of String) From {"", Nothing, "LOL", "Foo"}

        LookupControl23.DataSource = GetDatatable(100000)

        AddHandler LookupControl.SelectedValuesChanged, Sub(_sender As Object, SelectedValues As List(Of String))
                                                            MsgBox("Selected Values: " & String.Join(",", SelectedValues.ToArray))
                                                        End Sub

        AddHandler LookupControl21.SelectedValuesChanged, Sub(_sender As Object, SelectedValues As List(Of String))
                                                              MsgBox("Selected Values: " & String.Join(",", SelectedValues.ToArray))
                                                          End Sub

        AddHandler LookupControl22.SelectedValuesChanged, Sub(_sender As Object, SelectedValues As List(Of String))
                                                              MsgBox("Selected Values: " & String.Join(",", SelectedValues.ToArray))
                                                          End Sub
    End Sub

    Private Function GetDatatable(Limit As Integer) As DataTable
        Dim oDatatable As New DataTable
        Dim oColumns As New List(Of DataColumn) From {
            New DataColumn("Col1", GetType(String)),
            New DataColumn("Col2", GetType(String))
        }

        oDatatable.Columns.AddRange(oColumns.ToArray)

        For Each Item In _Datasource.Take(Limit)
            Dim oRow = oDatatable.NewRow()
            oRow.Item("Col1") = Item
            oRow.Item("Col2") = Item & "_" & "SomeLong Random(String) !!!111einself"
            oDatatable.Rows.Add(oRow)
        Next

        Return oDatatable
    End Function
End Class