CODEWITHSUNDEEP
c#asp.netvb.net
Milas
Milas

Reputation: 347

edit list collection problem : error note Collection was modified; enumeration operation may not execute

I have the following classes:

Product, Service and OrderItem

Product and Service must inherit OrderItem. So basically I want to store OrderItem object in my shopping cart and these object are store in a list.

Public MustInherit Class OrderItem
    Private m_enuItemType As TypeOfItem = TypeOfItem.None
    Private m_strUserID As Integer
    Private m_UserName As String
    Private m_Currency As String
    Private m_CurrencyType As Decimal
    Private m_MiniCartSubTotal As Decimal

    Public Sub New(ByVal enuItemType As TypeOfItem)
        m_enuItemType = enuItemType
    End Sub

    Public Enum TypeOfItem
        None = 0
        Product = 1
        Service = 2
    End Enum

    Public Property ItemType() As TypeOfItem
        Get
            Return m_enuItemType
        End Get
        Set(ByVal value As TypeOfItem)
            m_enuItemType = value
        End Set
    End Property
End Class

Class Product

Public Class CartProduct
    Inherits OrderItem

    Private Product_Id As String = ""
    Private Qty As Integer = Nothing
    Private price As String = ""
    Private priceFormat As String = ""
    Private UserPrice As Decimal = 0

    Public Sub New(ByVal enuItemType As TypeOfItem)
        MyBase.New(enuItemType)
    End Sub

    Public Property ProductId() As String
        Get
            Return Product_Id
        End Get
        Set(ByVal value As String)
            Product_Id = value
        End Set
    End Property

End Class

Here is my problem: When user add product, I want to verify if the product already exist in the List. If it does, I want to increment the value but I'm having an error. Here is my add orderItem code:

Public Function AddItem(ByVal objOrderItem As OrderItem) As Boolean

    Try

        If m_objArrListOfItems.Count > 0 Then

         ' Validate item to check if it is already in the list
        ' If yes, increment counter, otherwise add new item to the list

            Dim objValidateCartProduct As New CartProduct(OrderItem.TypeOfItem.Product)
            Select Case objOrderItem.ItemType
                Case OrderItem.TypeOfItem.Product
                    objValidateCartProduct = DirectCast(objOrderItem, CartProduct)
            End Select


            For Each p As CartProduct In m_objArrListOfItems
                If objValidateCartProduct.ProductId = p.ProductId Then
                    p.OrderQty = p.OrderQty + objValidateCartProduct.OrderQty

                Else
                    m_objArrListOfItems.Add(objOrderItem)
                End If

            Next


        Else
            m_objArrListOfItems.Add(objOrderItem)

        End If

    Catch ex As Exception
        MsgBox(ex.ToString)
        ' Log error
    End Try

End Function

Upvotes: 0

Views: 122

Answers (1)

James Johnson
James Johnson

Reputation: 46067

The easiest solution is to use a for loop for this kind of stuff. I haven't tested this code, but it should go something like this:

for (int i = 0; i < m_objArrListOfItems.Count; i++)
{
    Product p = m_objArrListOfItems[i];
    if (objValidateCartProduct.ProductID == p.ProductID)
    {
        p.OrderQty += objValidateCartProduct.OrderQty;
        break;
    }
    m_objArrListOfItems.Add(objOrderItem);        
}

VB.NET

EDIT: Changed Continue For to Exit For when a matching ProductID is found.

It sounds like you need to break out of the loop when a matching ProductID is found, so try this:

For i As Integer = 0 To m_objArrListOfItems.Count - 1
    Dim p As Product = m_objArrListOfItems(i)
    If objValidateCartProduct.ProductID = p.ProductID Then
        p.OrderQty += objValidateCartProduct.OrderQty
        Exit For
    End If
    m_objArrListOfItems.Add(objOrderItem)        
Next

Upvotes: 1

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