Public Class MainDemo
 
    Dim ds As New DataSet
    Dim WithEvents btnProject As New Button With {.Parent = Me, .Text = _
      "Projekt"}
 
    Private WithEvents _project As UF_Project
 
    Private Sub MainDemo_Load(sender As System.Object, _
        e As System.EventArgs) Handles MyBase.Load
 
        Dim dt As New DataTable
        dt.Columns.Add("Hallo") : dt.Columns.Add("Welt")
        dt.Rows.Add({"Ciao", "Saturn"})
        dt.Rows.Add({"Grüzi", "Merkur"})
        ds.Tables.Add(dt)
    End Sub
 
 
    Private Sub btnProject_Click(sender As Object, _
        e As System.EventArgs) Handles btnProject.Click
 
        If _project IsNot Nothing Then
            _project.Close()
        End If
 
        _project = New UF_Project
 
        With _project
            .ds = ds
            .Show()
        End With
    End Sub
End Class
 
 
Public Class UF_Project
 
    Dim _ds As DataSet
 
    Private bs1 As New BindingSource
    Private dgv As New DataGridView With _
           {.Parent = Me, .DataSource = bs1, .Top = 50}
    Private WithEvents btnMandant As New Button With _
           {.Parent = Me, .Text = "Mandant"}
 
    Public WriteOnly Property ds As DataSet
        Set(value As DataSet)
            _ds = value
            bs1.DataSource = _ds.Tables(0)
            bs1.ResetBindings(True)
        End Set
    End Property
 
    Private Sub btnMandant_Click(sender As Object, _
        e As System.EventArgs) Handles btnMandant.Click
 
        Using _mandant As New UF_Mandant
            _mandant.ds = _ds
            _mandant.ShowDialog()
        End Using
    End Sub
 
End Class
 
 
Public Class UF_Mandant
 
    Dim _ds As DataSet
 
    Private bs1 As New BindingSource
    Private dgv As New DataGridView With _
           {.Parent = Me, .DataSource = bs1, .Top = 50}
 
    Public WriteOnly Property ds As DataSet
        Set(value As DataSet)
            _ds = value
            bs1.DataSource = _ds.Tables(0)
            bs1.ResetBindings(True)
        End Set
    End Property
 
End Class