Why is my extension not sorting the List(Of String)?-CodePudding

I have written the following extension:

<Extension>
Public Sub SortByLengthDescending(ByVal uList As List(Of String))

    uList.OrderByDescending(Function(c) c.Length)

End Sub

The list of string looks like this:

[0] = "short text"
[1] = "very very very very long text"

I expect the function to sort the list so that it looks like this:

[0] = "very very very very long text"
[1] = "short text"

But that doesn't happen.

Here is my code:

    Dim nTest As New List(Of String)
    nTest.Add("short text")
    nTest.Add("very very very very long text")

    nTest.SortByLengthDescending

What am I missing?

Edit:

I have now found this:

<Extension>
Public Sub SortByLengthDescending(ByVal uList As List(Of String))

    Dim comparison As Comparison(Of String) =
            Function(x, y)
                Dim rslt = x.Length.CompareTo(y.Length)
                Return If(rslt = 0, rslt, x.CompareTo(y))
            End Function
    uList.Sort(comparison)

End Sub

But even this does not work right.

Here are the results:

In this example one can see that [5] is indeed longer than

Thank you!

CodePudding user response：

You need to use ByRef to change the original list:

Imports System.Runtime.CompilerServices

Module ListExtensions
    <Extension>
    Sub OrderByLengthDescending(ByRef stringList As List(Of String))
        stringList = stringList.OrderByDescending(Function(s) s.Length).ToList()
    End Sub

End Module

So...

Module Module1

    Sub Main()
        Dim a As New List(Of String) From {"AB", "ABC", "A"}
        a.OrderByLengthDescending()
        Console.WriteLine(String.Join(", ", a))

        Console.ReadLine()

    End Sub

End Module

Outputs:

ABC, AB, A

CodePudding user response：

You need to get the reference to that object. You're taking its value. This link explains it well.