Public Class Form1
    Private _Datasource As New List(Of String) From {"Foo", "bar", "baz", "quux"}

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load

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

        LookupControl.DataSource = oDatatable
        LookupControl.SelectedValues = oSelectedValues
    End Sub

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

        oDatatable.Columns.AddRange(oColumns.ToArray)

        For Each Item In _Datasource
            Dim oRow = oDatatable.NewRow()
            oRow.Item("Col1") = Item
            oDatatable.Rows.Add(oRow)
        Next


        Return oDatatable
    End Function

    Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
        MsgBox(LookupControl.SelectedValues.Count)
    End Sub
End Class