通过 vb.net 中的 foreach 循环在列表中插入 class 属性

Question

I am trying to insert class property in list through foreach loop in VB.NET.

Dim objCoInsurers As List(Of CoInsurer)

CoInsurer class consist of 5 properties

Below there is the code where class properties are inserted in my list

 objCoInsurers = New List(Of CoInsurer)
 Dim oCoInsurer As New CoInsurer
 For Each row As GridViewRow In grdCoInsurance.Rows
  Dim lblCoInsurerID = DirectCast(row.FindControl("lblCoInsurerID"), Label)
  Dim textCoInsurerID As String = lblCoInsurerID.Text
  Dim lblCoInsurerName = DirectCast(row.FindControl("lblCoInsurerName"), Label)
  Dim CoInsurerName As String = lblCoInsurerName.Text
oCoInsurer.InsurerID = lblCoInsurerID.Text
oCoInsurer.InsurerName = lblCoInsurerName.Text
 objCoInsurers.Add(oCoInsurer)
Next

The issue is when two list containing same value, the first list overwrite the second one, if row count is 2 in gridview or more

Answer 1

Consider this. Let's say that you want to add people to a list using pen and paper. I present myself to you wearing a blue shirt and you write down my name. I then take off my blue shirt and put on a red shirt and present myself to you and you write down my name. I then take off my red shirt and put on a green shirt and present myself to you and you write down my name. How many names do you have on the list? How many people do those names correspond to? What colour shirt do the people those names correspond to have on?

Given that OOP is based on the behaviour of real-world objects, think about what your code actually does. How many ColInsurer objects does your code create? Only one, right? It doesn't matter how many different colour shirts you put on that object and how many times you add it to the list, there's still only one object so it can only be wearing one shirt at a time. At the end of your loop, every item in the list refers to the same object and that object will have whatever property values you set last.

If you want to add multiple distinct objects to the list then you actually have to create multiple distinct objects. That means moving the creation of the object inside the loop, so it happens every iteration. You create a new object, set its properties and then add it to the list:

For Each row As GridViewRow In grdCoInsurance.Rows
    Dim oCoInsurer As New CoInsurer

Answer 2

I am guessing your class looks something like this.

Public Class CoInsurer
    Public Property InsurerID As String
    Public Property InsurerName As String
End Class

I am wondering if InsurerID is a String and not an Integer or Long . If it is a number, be sure to surround the assignment value in the loop with CInt() or CLng()

I got rid of some of the unneeded variables. As jmcilhinney explained, you need to create a new instance of CoInsurer for every iteration of your loop.

Private Sub OPCode()
    For Each row As GridViewRow In grdCoInsurance.Rows
        Dim oCoInsurer As New CoInsurer
        oCoInsurer.InsurerID = DirectCast(row.FindControl("lblCoInsurerID"), Label).Text
        oCoInsurer.InsurerName = DirectCast(row.FindControl("lblCoInsurerName"), Label).Text
        objCoInsurers.Add(oCoInsurer)
    Next
End Sub