. In addition, <T> throws an exception

Question

I have the following code:

Public Shared Function GetAvailableManufacturers() As List(Of Manufacturer)
    'first get all the live orders and extract their mfrs'
    Dim sos As List(Of OrderForm) = GetFormsByStatus(StockStatus.Building)
    Dim unavailableMfrs As New List(Of Manufacturer)
    For Each so As StockingOrder In sos
        unavailableMfrs.Add(so.Source)
    Next

    'then remove all mfrs with an open SO from a list of all mfrs'
    Dim allMfrs As List(Of Manufacturer) = Manufacturer.GetManufacturers
    Return allMfrs.Except(unavailableMfrs) <----- error here
End Function

Explanation of what is doing above:

• GetFormsByStatus() self-evident
• GetManufacturers() returns a list of all manufacturers in the database

My idea of ​​accessing manufacturers was to get a list of all manufacturers in my open forms, and then get a list of all manufacturers and exclude all manufacturers in the first list, illustrated as follows (pseudo):

List A: {1,2,3,4,5,6,7,8,9,10}
List B: {5,7,10}
Result: {1,2,3,4,6,8,9}

I set my class Manufactureraccording to this article so that it can be compared, but I still get this error:

Unable to pass an object of type ' <ExceptIterator>d__92'1[csCore.Manufacturer]'for input System.Collections.Generic.List'1[csCore.Manufacturer]'.

, , GetFormsByStatus() 0 , , , , Except() , 0 . - , ?

!

Answer 1

List (Of Manufacturer), IEnumerable (Of Manufacturer), .ToList() :

Return allMfrs.Except(unavailableMfrs).ToList()

Answer 2

(), Return IEnumerable (Of Manufacturer). return :

Return allMfrs.Except(unavailableMfrs).ToList()

Strict On, , VB ​​ , .

Answer 3

The problem is that Enumerable.Except returns IEnumerable<T>, but your return type List(Of T).

Change your last line to:

Return allMfrs.Except(unavailableMfrs).ToList()