Lambda Tutorial and Solving a Lambda-Function

Question

Is it possible to shorten the following function to a lambda expression?

Or (to do the trick by myself) what is the best and most understandable for beginners tutorial for lambda in vb.net?

Function getit(ByVal wert As Integer, ByVal sk As Integer, ByVal list As List(Of Array)) As String
    Dim ergebnis As String
    ergebnis = "Null"
    For Each strg As String() In list
        If wert >= Integer.Parse(strg(0)) And wert < Integer.Parse(strg(0)) + 5 And sk = Integer.Parse(strg(1)) Then
            Return strg(2)
        End If
    Next
    Return ergebnis
End Function

Answer 1

Give this a try:

Dim getit As String;

getit = (From x In list
         Where (wert >= Integer.Parse(x(0))) AndAlso (wert < Integer.Parse(x(0)) + 5) AndAlso (sk = Integer.Parse(x(1)))
         Select x(2)).Union(Of String)(New List(Of String) { "Null" }).First(Of String)()

Answer 2

You could create a lambda expression which takes a string array and return True if it fulfills the condition:

Dim isValidArray = Function(strg as String()) _
                     wert >= Integer.Parse(strg(0)) AndAlso _
                     wert < Integer.Parse(strg(0)) + 5 AndAlso _
                     sk = Integer.Parse(strg(1))

I would also change the signature of your method to accept a list of string array instead of a list of any array. The final code would be:

Function getit(ByVal wert As Integer, ByVal sk As Integer, _
               ByVal list As List(Of String())) As String

    ''//Insert above lambda here

    ''//Get first valid item or default (Nothing) if no valid item
    Dim validArray As String() = list.FirstOrDefault(isValidArray)

    If validArray IsNot Nothing
        Return validArray(2)
    Else
        Return "Null"
    End If
End Function