DataGridView 级联/相关组合框列

Question

因此，我不时在 Winforms 中处理遗留应用程序，并且并不熟悉绑定对象的最佳实践。基本上，我有一个由三个部分组成的套装，其中有两个人，他们可能只有一个产品，但该产品可能会导致有不同的 SKU 集。有没有办法从第一个组合框的值触发组合框的事件和填充？我一直在环顾四周，我正在寻找有关如何绑定组合框的基本数据（我可以做到这一点），或者对如何绑定它做一些事情。触发依赖父项更改并更改数据集后不绑定。下面的例子：

POCOS：

Public Class Person
  Public Property PersonID As Integer
  Public Property FirstName As String
  Public Property LastName As String
  Public Property ProductId As Integer
  Public Property SkuId As Integer
End Class

Public Class Product
  Public Property ProductId As Integer
  Public Property Description As String
End Class

Public Class Sku
  Public Property SKUId As Integer
  Public Property ProductId As Integer
  Public Property Description As String
End Class

主要代码示例（基本 UI 实际上只有一个标记为“ds”的数据集，该数据集与具有数据表的人员和产品 POCOS 几乎完全相同。数据网格视图“dgv”的列绑定到人员中的数据，除了名为 SKU 的列没有绑定因为我想在事后绑定它，这就是我失败的地方。

2016 年 9 月 13 日更新 我可以让下面的代码在某些大型解决方案中工作除外（我这样做的全部原因）。它基本上不会执行将 cell() 转换为 a 的行datagridviewcomboboxcell并忽略它并跳过该行。没有理由，它只是跳过它。我想知道在较大的类中数据网格视图是否会损坏或其他什么。

主要代码：

Private _people As List(Of Person) = New List(Of Person)
Private _products As List(Of Product) = New List(Of Product)
Private _SKUs As List(Of Sku) = New List(Of Sku)
Private _initialLoadDone = False
Private _currentRow As Integer? = Nothing

Private Sub DynamicComboBoxDoubleFill_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    _products = New List(Of Product)({
                                     New Product With {.ProductId = 1, .Description = "Offline"},
                                     New Product With {.ProductId = 2, .Description = "Online"}
                                     })

    Dim s = ""
    For Each o In _products
      Dim row As DataRow = ds.Tables("tProducts").NewRow
      row("ProductId") = o.ProductId
      row("Description") = o.Description
      ds.Tables("tProducts").Rows.Add(row)
    Next

    _SKUs = New List(Of Sku)({
     New Sku With {.SKUId = 1, .ProductId = 1, .Description = "Mail"},
     New Sku With {.SKUId = 2, .ProductId = 1, .Description = "Magazine"},
     New Sku With {.SKUId = 3, .ProductId = 2, .Description = "Email"},
     New Sku With {.SKUId = 4, .ProductId = 2, .Description = "APIRequest"}
    })

    Dim items = _SKUs

    _people = New List(Of Person)({
      New Person With {.PersonID = 1, .FirstName = "Emily", .LastName = "X", .ProductId = 1, .SkuId = 1},
      New Person With {.PersonID = 2, .FirstName = "Brett", .LastName = "X", .ProductId = 2, .SkuId = 3}
                                  })
    For Each p In _people
      Dim row As DataRow = ds.Tables("tPeople").NewRow
      row("PersonId") = p.PersonId
      row("FirstName") = p.FirstName
      row("LastName") = p.LastName
      row("ProductId") = p.ProductId
      row("SkuId") = p.SkuId
      ds.Tables("tPeople").Rows.Add(row)
    Next

    For Each row As DataGridViewRow In dgv.Rows
      ArrangeValuesForSKUComboBox(row)
    Next

    _initialLoadDone = True
  End Sub

  Private Sub ArrangeValuesForSKUComboBox(row As DataGridViewRow)
    Dim productId = CInt(row.Cells("ProductId")?.Value)
    Dim skus = _SKUs.Where(Function(x) x.ProductId = productId).ToList().Select(Function(x) New With {Key .SkuId = x.SKUId, .SkuDesc = x.Description}).ToList()

    Dim cell = row.Cells("SKU")
    'Yeah I don't always work.  In this example I do, in others I won't.
    'For this reason I just want more ideas.  I don't care if you completely blow up how the binding is done and do something else entirely.
    Dim combobox = CType(cell, DataGridViewComboBoxCell)
    combobox.DataSource = skus
    combobox.ValueMember = "SKUId"
    combobox.DisplayMember = "SkuDesc"
    combobox.Value = skus.FirstOrDefault()?.SkuId
  End Sub

  Private Sub dgv_CellValueChanged(sender As Object, e As DataGridViewCellEventArgs) Handles dgv.CellValueChanged
    If _initialLoadDone Then
      Dim headerText As String = TryCast(sender, DataGridView).Columns(e.ColumnIndex).HeaderText
      If headerText = "PRODUCT" Then
        ArrangeValuesForSKUComboBox(dgv?.CurrentRow)
      End If
    End If
  End Sub

Answer 1

要在 中有从属（级联或主/从）ComboBox列DataGridView，您可以按照以下步骤操作：

1. 一组DataSource从列到所有可用值。

   目标：这里的目标是防止首次加载时出现渲染错误，因此所有从属组合框都可以正确显示值。

2. EditingControlShowing网格的Hanlde事件并检查当前单元格是否为从属组合单元格，然后使用e.Control类型为的编辑控件获取DataGridViewComboBoxEditingControl。然后检查主组合单元格的值，并根据主组合单元格的值将DataSource编辑控件的属性设置为合适的值子集。如果主单元格的值为空，则将数据源设置为空。

   目标：这里的目标是设置从属组合的数据源，以便在从从属组合中选择值时仅显示合适的值。

3. 处理CellValueChanged并检查当前单元格是否为主组合，然后将依赖单元格的值设置为空。
   注意：您可以根据主单元值将其设置为第一个可用的有效值，而不是将从单元的值设置为空。

   目标：这里的目标是防止主combo的值改变后slave的combo有无效的值，所以我们重新设置了这个值。

遵循上述规则，您可以根据需要拥有任意数量的相关组合框。

例子

在下面的示例中，我有一个 Country (Id, Name) 表、一个 State(Id, Name, CountryId) 表和一个 Population(CountryId, StateId, Population) 表。我想使用国家和州的 2 个组合列和人口的文本列来执行人口表的数据输入。我知道这不是一个正常的数据库设计，但它只是例如在网格中有主/从（从属）组合框列：

Private Sub EditingControlShowing(sender As Object, _
    e As DataGridViewEditingControlShowingEventArgs) _
    Handles PopulationDataGridView.EditingControlShowing

    Dim grid = DirectCast(sender, DataGridView)
    If (grid.CurrentCell.ColumnIndex = 1) Then 'State column
        Dim combo = DirectCast(e.Control, DataGridViewComboBoxEditingControl)
        If (grid.CurrentRow.Cells(0).Value IsNot DBNull.Value) Then
            Dim data = Me.DataSet1.State.AsDataView()
            data.RowFilter = "CountryId = " + grid.CurrentRow.Cells(0).Value.ToString()
            combo.DataSource = data
        Else
            combo.DataSource = Nothing
        End If
    End If
End Sub

Private Sub CellValueChanged(sender As Object, e As DataGridViewCellEventArgs) _
    Handles PopulationDataGridView.CellValueChanged
    Dim grid = DirectCast(sender, DataGridView)
    If (e.ColumnIndex = 0 And e.RowIndex >= 0) Then 'Country Column
        grid.Rows(e.RowIndex).Cells(1).Value = DBNull.Value 'State Column 
    End If
End Sub