Lambda Tutorial and Solving a Lambda-Function

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 tuto开发者_如何学Gorial 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

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

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)()