DataGridView Cascading/Dependent 组合框列

Question

所以我时不时地在 Winforms 中处理遗留应用程序，并不总是熟悉绑定对象的最佳实践。基本上我有一个三部分集，我有两个人，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，要么找到关于如何绑定组合框的基本数据（我可以做到这一点），要么对你如何绑定它做一些事情。在触发依赖父更改并更改数据集后不绑定。示例如下：

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 Datset，它几乎完全匹配具有数据表的 Person 和 Product POCOS。一个 datagridview 'dgv' 其列绑定到Person 中的数据，除了名为 SKU 的列没有绑定，因为我想事后绑定它，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（我这样做的全部原因）。它基本上不会执行将 cell() 转换为 datagridviewcomboboxcell 的行并忽略它并跳过该行。没有为什么，它只是跳过它。我想知道在更大的类中，数据网格视图是否会损坏或发生其他问题。

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 DataGridView 中具有依赖（级联或 master/slave）ComboBox 列，您可以按照以下步骤操作：

将从属列的 DataSource 设置为所有可用值。

目标：这里的目标是防止第一次加载时出现渲染错误，所以所有的从属组合框都可以正确显示值。
Hanlde EditingControlShowing 事件并检查当前单元格是否为从组合单元格，然后使用 e.Control 类型的 DataGridViewComboBoxEditingControl 获取编辑控件].然后检查主组合单元格的值，并根据主组合单元格的值将编辑控件的DataSource 属性设置为一个suitable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slave combo的数据源在选择值时只显示suitable值来自奴隶组合。
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：您可以根据主单元格值将其设置为第一个可用的有效值，而不是将从单元格的值设置为空。

目标：这里的目标是防止master combo的值改变后slave combo有无效值，所以我们重新设置值。

按照以上规则，您可以根据需要拥有任意数量的依赖组合框。

例子

在下面的示例中，我有一个国家 (Id, Name) table、一个州 (Id, Name, CountryId) table 和一个人口 (CountryId, StateId, Population) table.我想为人口 table 执行数据输入，使用国家和州的 2 个组合列和人口的文本列。我知道这不是正常的数据库设计，但这只是在网格中具有 master/slave（相关）组合框列的示例：

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

DataGridView Cascading/Dependent 组合框列

DataGridView Cascading/Dependent ComboBox Columns

vb.net

data-binding

datagridview

datagridviewcombobox

winforms