vb.net - .Net DataSet 不适合设计时

Question

我写了一个自定义数据集(基于强类型数据集，我进一步了解)我想让它适合在设计时使用，比如从工具箱中拖拽(作为数据集工具自动生成) .所有这一切都在发生，因为我试图保留我的同事设定的开发方法(我是新来的，哈哈哈)，当然我知道 Entity Framework 的存在和类似的东西。因此，当我将它放在我的表单上时出现此错误:

Relation named 'ParentChild_Relation' already belongs to this DataSet

当然是物质关系

这是代码:

Public Class MyDataSet
    Inherits DataSet

    Public Const PARENTCHILD_RELATION As String = "ParentChild_Relation"

    Public Sub New()
        MyBase.New()
        Me.BeginInit()
        Me.CreateDataSet()
        Me.EndInit()
    End Sub

    Private Sub CreateDataSet()
        DataSetName = "Test"
        Me.EnforceConstraints = True
        Me.Tables.Add(New ParentTable) 'custom datatable
        Me.Tables.Add(New ChildTable) 'custom datatable

        CreateRelation()
    End Sub

    Private Sub CreateRelation()
        With DirectCast(Me.Tables(ChildTable.TABLENAME).Constraints.Add(PARENTCHILD_RELATION ,
                                                                Me.Tables(ParentTable.TABLENAME).Columns(ParentTable.ID),
                                                                Me.Tables(ChildTable.TABLENAME).Columns(ChildTable.ID)), ForeignKeyConstraint)
            .UpdateRule = Rule.Cascade
            .DeleteRule = Rule.Cascade
            Me.Relations.Add(.ConstraintName, .RelatedColumns, .Columns, False)
        End With
    End Sub

End Class

我会知道任何可能的帮助

编辑

没有这一行也能工作:

Me.Relations.Add(.ConstraintName, .RelatedColumns, .Columns, False)

但是，我仍然想要 DataSet 关系，因为这是它们的工作方式

编辑 2

没有上一行，它不会通过绑定(bind)找到关系:

BindingSource.DataSource = New MyDataSet
BindingSource.DataMember = "ParentChild_Relation"

Answer 1

我必须这样做:实现 DataSet.Initialized 事件，然后在其中创建所有关系。

Public Class MyDataSet
    Inherits DataSet

    Public Const PARENTCHILD_RELATION As String = "ParentChild_Relation"

    Public Sub New()
        MyBase.New()
        Me.CreateDataSet()  
        With DirectCast(Me.Tables(ChildTable.TABLENAME).Constraints.Add(PARENTCHILD_RELATION ,
                                                                Me.Tables(ParentTable.TABLENAME).Columns(ParentTable.ID),
                                                                Me.Tables(ChildTable.TABLENAME).Columns(ChildTable.ID)), ForeignKeyConstraint)
            .UpdateRule = Rule.Cascade
            .DeleteRule = Rule.Cascade
        End With
        AddHandler Initialized, AddressOf InitializedHandler
    End Sub        


    Private Sub InitializedHandler(sender As Object, e As EventArgs)            
        Relations.AddRange((From tb As DataTable In Tables
                        From fkc As ForeignKeyConstraint In tb.Constraints.OfType(Of ForeignKeyConstraint)()
                        Where Not Relations.Contains(fkc.ConstraintName)
                        Select New DataRelation(fkc.ConstraintName, fkc.RelatedColumns, fkc.Columns, False)).ToArray())
    End Sub

    Private Sub CreateDataSet()
        DataSetName = "Test"
        Me.EnforceConstraints = True
        Me.Tables.Add(New ParentTable) 'custom datatable
        Me.Tables.Add(New ChildTable) 'custom datatable
    End Sub

End Class

我认为这对其他人有帮助