Public Class frmCreateTable
 
    Dim WithEvents dt As New DataTable
 
    Dim lblCreateColumn As New Label With
        {.Parent = Me, .Text = "  Spalte erstellen: ", _
         .AutoSize = False, .Width = 120}
    Dim WithEvents cboCreateColumn As New ComboBox With
        {.Parent = Me, .Left = 125, _
         .DropDownStyle = ComboBoxStyle.DropDownList}
 
 
    Dim WithEvents dgv As New DataGridView With _
        {.Parent = Me, .Top = 40, .Width = 400}
 
 
    Private Sub frmCreateTable_Load(sender As Object, _
        e As EventArgs) Handles MyBase.Load
        With cboCreateColumn.Items
            .Add("Boolean")
            .Add("Integer")
            .Add("Decimal")
            .Add("Bitmap")
            .Add("String")
        End With
        cboCreateColumn.SelectedIndex = 0
 
        Dim dc As DataColumn = dt.Columns.Add("Key", GetType(Integer))
        dc.ReadOnly = True
    End Sub
 
 
    Private Sub AddColumn()
 
        Dim cn As String = _
           InputBox("Bezeichnung der Spalte", "Spalte erstellen", "")
        If String.IsNullOrWhiteSpace(cn) Then Exit Sub
        If dt.Columns.Contains(cn) Then Exit Sub
 
        Dim r1 As DialogResult = DialogResult.No
        If dt.Rows.Count = 0 Then
            r1 = MsgBox _
              ("Spalte " & cn & "   Nullwerte zulassen?", MsgBoxStyle.YesNo)
        End If
 
        Dim r2 As DialogResult =
            MsgBox _
            ("Spalte " & cn & "   Eindeutige Werte notwendig?", _
            MsgBoxStyle.YesNo)
 
        Dim dc As DataColumn
        With dt.Columns
            Select Case cboCreateColumn.SelectedItem
                Case "Boolean"
                    dc = .Add(cn, GetType(Boolean))
                Case "Integer"
                    dc = .Add(cn, GetType(Integer))
                Case "Decimal"
                    dc = .Add(cn, GetType(Decimal))
                Case "Bitmap"
                    dc = .Add(cn, GetType(Bitmap))
                Case Else
                    dc = .Add(cn, GetType(String))
            End Select
        End With
 
        dc.AllowDBNull = r1 = DialogResult.Yes
        dc.Unique = r2 = DialogResult.Yes
        dgv.DataSource = dt
    End Sub
 
 
    Private Sub cboCreateColumn_DropDownClosed(sender As Object, e As _
      EventArgs) _
        Handles cboCreateColumn.DropDownClosed
        AddColumn()
    End Sub
 
 
    Private Sub dgv_DataError(sender As Object, e As _
      DataGridViewDataErrorEventArgs) _
        Handles dgv.DataError
 
        MsgBox(e.Exception.Message)
        e.Cancel = True
    End Sub
 
 
    Private Sub dt_TableNewRow(sender As Object, e As DataTableNewRowEventArgs) _
        Handles dt.TableNewRow
 
        If dt.Rows.Count = 0 Then
            e.Row.Item(0) = 1
        Else
            Dim k As Integer = 0
            For i As Integer = 0 To dt.Rows.Count - 1
                k = Math.Max(k, CInt(dt.Rows(i).Item(0)))
            Next i
            k += 1
            e.Row(0) = k
        End If
    End Sub
End Class