如何在VB.NET中实现用户控件向Windows窗体传递数据

现有代码中，子窗体仅在Populate方法执行时从用户控件获取一次mUniqueTransId，但用户点击网格按钮触发SelectCard更新用户控件的mUniqueTransId时，子窗体的对应属性不会同步更新，导致父窗体拿到的是初始值而非选中后的最新值。以下是修正方案：

步骤1：给用户控件添加选中事件 #

在用户控件中定义事件，选中记录并获取mUniqueTransId后触发事件传递值：

' 用户控件中新增事件定义
Public Event CardSelected(ByVal uniqueTransId As String)

Private Sub SelectCard(ByVal RecordIdentity As Integer)
    Try
        Dim selectedItem = (From d In mCustomerPaymentDetailsList Where d.Identity = RecordIdentity).FirstOrDefault()
        If selectedItem IsNot Nothing Then
            mUniqueTransId = selectedItem.UniqueTransId
            ' 触发事件，传递选中的UniqueTransId
            RaiseEvent CardSelected(mUniqueTransId)
        End If
    Catch ex As Exception
        Charter.UI.ApplicationBase.Utility.ShowException(mUIC, "Edit Customer Cards", ex)
    End Try
End Sub

Private Sub lgMain_CellButtonClick(ByVal cell As Infragistics.Win.UltraWinGrid.UltraGridCell, ByVal ColumnName As String) Handles lgMain.CellButtonClick
    SelectCard(lgMain.SelectedId)
End Sub

步骤2：子窗体订阅用户控件事件并更新属性 #

在子窗体中订阅用户控件的CardSelected事件，实时更新自身的mUniqueTransId：

Public Class CustomerCardsDlg

    Private mUIC As ApplicationInterfaces.UIContext
    Private mPaymentDetailsList As New DataTable
    Private mCustomerCallerService As CustomerCallerService
    Private mCustomerPaymentDetailsList As List(Of CustomerGravityPaymentDetailsModel)
    Private mCustomerIdentity As Integer = Integer.MinValue
    Public Property mUniqueTransId As String = String.Empty

    Public Sub New(UIC As ApplicationInterfaces.UIContext, customerIdentity As Integer)
        InitializeComponent()
        mUIC = UIC
        mCustomerIdentity = customerIdentity
        mCustomerCallerService = New CustomerCallerService(UIC.Context.ProductKey, UIC.Context.UserName)
        ' 订阅用户控件的选中事件
        AddHandler PaymentMethodsEmergePayCtrl1.CardSelected, AddressOf OnCardSelected
    End Sub

    ' 处理用户控件的选中事件，更新自身属性
    Private Sub OnCardSelected(ByVal uniqueTransId As String)
        mUniqueTransId = uniqueTransId
        ' 若需要选中后直接关闭弹窗，可添加以下代码
        ' Me.Close()
    End Sub

    Private Sub Populate()
        Try
            PaymentMethodsEmergePayCtrl1.Populate(mUIC, mPaymentDetailsList, mCustomerPaymentDetailsList)
        Catch ex As Exception
            Charter.UI.ApplicationBase.Utility.ShowException(mUIC, "Could not load.", ex)
        End Try
    End Sub

    Private Async Sub Dlg_Shown(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Shown
        PaymentMethodsEmergePayCtrl1.Focus()
        mCustomerPaymentDetailsList = Await mCustomerCallerService.GetCustomerPaymentDetailsAsync(mCustomerIdentity)
        mPaymentDetailsList = Ops.Utility.ConvertToDataTable(mCustomerPaymentDetailsList)
        Populate()
    End Sub

End Class

步骤3：父窗体获取最新值 #

父窗体现有代码无需修改，当子窗体关闭后，f.mUniqueTransId会返回用户最后选中的记录ID；若在子窗体的OnCardSelected方法中添加Me.Close()，则选中后弹窗直接关闭，父窗体立即拿到选中值。

内容的提问来源于stack exchange，提问作者Kamran Khan