get last item in an list in vb.net

Question

User52515197 posted

This command returns the last object from the list without any condition for the search

My code:

aList.Last()

example :

    Structure group
        Public name

        Public Sub New(value As String)
            name = value
        End Sub
    End Structure

Dim listGroups As New List(Of group)

listGroups.Add(New group("group 1"))

Dim groupName As string = listGroups.Last().name

Answer 1

User2053451246 posted

What is your question?

Answer 2

User52515197 posted

How to get the last value in the list ?

This was a recurring question, but because the expiration date was over, I had to re-raise it.

Answer 3

User1120430333 posted

Dim groupName As string = listGroups(listGroups.count-1).name  

You are using the listGroup.count that is the total number of items in the list - 1, because that list is a 0 based index (total count - 1). You are also using the index to address an item in the list by its index (listItem(idx).property).

Answer 4

User-893317190 posted

This command returns the last object from the list without any condition for the search

From the sentence above, it seems that you want to get the last value with a specify condition.

If so, the method Last() also accept a Function as its parameter, you could specify the condition through the Function using a bool expression.

Below is my code.

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        Dim listGroups As New List(Of group)

        listGroups.Add(New group("group 1"))
        listGroups.Add(New group("group 2"))
        listGroups.Add(New group("group 3"))
        listGroups.Add(New group("group 4"))
        listGroups.Add(New group("group 5"))
        Response.Write(listGroups.Last(Function(m) m.name = "group 4").name)


    End Sub

    Structure group
        Public name

        Public Sub New(value As String)
            name = value
        End Sub
    End Structure

The result.

For more information about use Function as a parameter , you could refer to

https://docs.microsoft.com/en-us/dotnet/visual-basic/programming-guide/language-features/procedures/lambda-expressions

Best regards,

Ackerly Xu

Answer 5

User52515197 posted

Thank you for your guidance
But how can I find it when I'm not aware of the content of the last item on the list

Answer 6

User1120430333 posted

zokaee hamid

Thank you for your guidance
But how can I find it when I'm not aware of the content of the last item on the list

List.Count is the total number of items in the list. List.Count-1  is going to be the last item in the list. Do the math and the last object in the list can be accessed by its index in the list.

dim name = list(idx number).name

dim name = list(0).name   'gets the name property of the first  object in the list.

list(1).name = 'zokaee hamid' sets the property of the second object in the list

All you are trying to do is get access to last object in the list. Does it need to be complicated by not using the object's index number in the list?

Answer 7

User52515197 posted

If the list is empty, the negative value will be entered

Answer 8

User1120430333 posted

zokaee hamid

If the list is empty, the negative value will be entered

If there are no items in the list, the list.count will equal 0. So you have to check the list.count before you try using an indexer in order to address an item in the list by its index in the list.

If List.Count() > 0 then

    '' address an item in the list by its index

endif