VB.net 在 For Each 循环中更新列表变量

Question

Dim aProductos As List(Of Producto)
Dim aRegistros As New List(Of Registro)
Dim selectedProd As New Producto

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    'Add to cart
    Dim insert As Boolean = True

问题从这里开始 vvv

    For Each reg In aRegistros
        If (reg.id_prod = Integer.Parse(lbCodigo.Text)) Then

            Dim r As New Registro
            r.id_prod = reg.id_prod
            r.cantidad = reg.cantidad + Integer.Parse(nudUni.Value.ToString)
            reg = r
            insert = False
        End If
    Next

问题在这里结束^^^

    If insert Then
        Try
            Dim r As New Registro
            r.id_prod = selectedProd.cod
            r.cantidad = Integer.Parse(nudUni.Value.ToString)
            aRegistros.Add(r)
        Catch ex As Exception
            MsgBox("Create and insert register: " + ex.Message)
        End Try
    End If
    MostrarFactura()
End Sub

Private Sub MostrarFactura() << Updates a listview to see the products you got
    listaProd.Items.Clear()
    For Each registro In aRegistros
        For Each producto In aProductos
            If registro.id_prod = producto.cod Then
                MsgBox(registro.cantidad)
                listaProd.Items.Add(producto.nombre + " --- " + registro.cantidad.ToString + " -> " + (producto.precio * registro.cantidad).ToString + "€")
            End If
        Next
    Next
End Sub

问题是我更新了“reg”，但是当循环完成时，reg 没有更新列表中的值

提前致谢：S

Answer 1

您可以使用整数来指定列表中的位置，而不是使用For Each。

For x = 0 to aRegistros.Count -1
  Dim reg = aRegistros(x)
  Dim r As New Registro
  r.id_prod = reg.id_prod
  r.cantidad = reg.cantidad + Integer.Parse(nudUni.Value.ToString)
  aRegistros(x) = r
  insert = False
Next