VB.NET Short Form Lambda Syntax

Question

I'm required by my company to use VB.NET rather than C#. It's not really that different of course, especially under the hood.

When it comes to lambdas, the long form I find frustrating. I haven't yet found if there's any short form syntax for lamdbas in VB.NET. Does that exist?

for example look how much shorter this is

ctx.Load(list.RoleAssignments, items => items.Include(
                         item => item.Member.LoginName,
                         item => item.Member.PrincipalType,
                         item => item.Member.Title));

than this

ctx.Load(list.RoleAssignments, Function(rac As RoleAssignmentCollection) rac.Include( _
                                                Function(item As RoleAssignment) item.Member.LoginName, _
                                                Function(item As RoleAssignment) item.Member.PrincipalType, _
                                                Function(item As RoleAssignment) item.Member.Title))

@Dai the languages are nearly identical... and I'm not sure what's "long" about writing the word function but here we are... — Jacob H
– Jacob H, Commented Feb 6, 2018 at 18:51
After a while of VB.NET, you'll find the "shortness" of C# weird... — the_lotus
– the_lotus, Commented Feb 6, 2018 at 19:08
You can cut out more verbosity by removing the As RoleAssignment from your VB, as VB can infer the parameter types just as C# can. Then it's just a matter of Function(item) instead of item =>. (And similarly the As RoleAssignmentCollection from the outer lambda.) — Craig
– Craig, Commented Feb 7, 2018 at 21:53

AJD · Accepted Answer · 2018-02-06 19:07:33Z

1

Yes, a short search for VBA(^) lambda came up with Microsoft Docs Lambda Expressions. To quote:

You create lambda expressions by using the Function or Sub keyword, just as you create a standard function or subroutine. However, lambda expressions are included in a statement.

The referenced site even includes useful examples. The following code is shamelessly cut and paste from the Microsoft site: Module Module2

Sub Main()
    ' The following line will print Success, because 4 is even.
    testResult(4, Function(num) num Mod 2 = 0)
    ' The following line will print Failure, because 5 is not > 10.
    testResult(5, Function(num) num > 10)
End Sub

' Sub testResult takes two arguments, an integer value and a 
' delegate function that takes an integer as input and returns
' a boolean. 
' If the function returns True for the integer argument, Success
' is displayed.
' If the function returns False for the integer argument, Failure
' is displayed.
Sub testResult(ByVal value As Integer, ByVal fun As Func(Of Integer, Boolean))
    If fun(value) Then
        Console.WriteLine("Success")
    Else
        Console.WriteLine("Failure")
    End If
End Sub

End Module

I don't do lambdas myself, I prefer fully qualified functions and subs - after all, they also do not take up much space and enhance readability of the code.

(^) Yes, I know I typed VBA instead of VB.Net, force of habit.

edited Feb 6, 2018 at 19:07

answered Feb 6, 2018 at 18:50

AJD

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2 Comments

Ctznkane525 Over a year ago

i added to my question...wondering if there's a short form in VB.NET

AJD Over a year ago

Edited to provide an example along the lines you have asked. However, the linked website includes all of this.

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