Get the sum of distinguishable values from a list in VB.Net
I have a list named Cart_Items and it populates when the Add to Cart button is clicked. The list contains the ItemID and Quantity objects. I need to get the total number of items from this list. Since there are different items in the list, I cannot get the total of a specific item. if i use sum (function) it returns the sum of all values. And what I'm trying to achieve is that if there is more than one record of the same item then get the SUM of that number of a specific item. here is the class structure:
Public Class CartItem
Private m_ItemId As Integer
Public Property ItemId() As Integer
Get
Return m_ItemId
End Get
Set(value As Integer)
m_ItemId = value
End Set
End Property
Private m_Quantity As Integer
Public Property Quantity() As Integer
Get
Return m_Quantity
End Get
Set(value As Integer)
m_Quantity = Value
End Set
End Property
End Class
List:
ItemId Quantity
1 5
3 6
1 2
1 6
4 8
so I want to get the total ItemId = 1, which should be 13.
So what would be the best way to get the total for a specific itemId? Thank.
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First, filter the items with a given criterion, which in this case CartItems
has itemId
of 1
. Then select all values and apply distinct
to remove duplicate values and finally the sum
result.
Dim result As Integer = (From item In myList
Where item.ItemId = 1
Select item.Quantity).Distinct().Sum()
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You need to collect all the elements according to them Id
, calculate the amount Quantity
for each group.
var itemTotals = myList.GroupBy(Function(item) item.ItemId)
.Select(Function(group)
Return New With
{
.ItemId = group.Key,
.Quantity = group.Sum(Function(item) item.Quantity)
}
End Function)
.ToList()
So, you will get a collection of anonymous objects with all the elements in myList
and their sums.
{ .ItemId = 1, Quantity = 13 } { .ItemId = 3, Quantity = 6 } { .ItemId = 4, Quantity = 8 }
Instead of anonymous types, you can use your class CartItem
because it has the same properties in the same context. Therefore, Select
pert will look like this:
.Select(Function(group)
Return New CartItem With
{
.ItemId = group.Key,
.Quantity = group.Sum(Function(item) item.Quantity)
}
End Function)
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