[RESOLVED] Lambda Expression Confusion

Hi all,
I've been wondering about lambda expressions for a while now.
Consider the following code

vb.net Code:

Sub Main()
        Dim I As Integer
        SomeUselessSub(Sub()
                           Dim K As Integer = I
                       End Sub)
 
        SomeUselessSub(New Action(AddressOf DoSomething))
    End Sub
    Sub DoSomething()
 
    End Sub
 
    Sub SomeUselessSub(ByVal D As [Delegate])
 
    End Sub

Both

Code:

---

        SomeUselessSub(Sub()
                          Dim K As Integer = I
                      End Sub)

---

And

Code:

---

SomeUselessSub(New Action(AddressOf DoSomething))

---

Are valid calls to SomeUselessSub.
But in the lambda expression I have access to all Sub Main's variables. Is it safe to use them ?

Since you can only use those variables in the lambda when calling the lambda from Sub Main, I would say yes it is safe to use them. It is really no different than passing them in as byref parameters (for value types) or simply just passing them in (for reference types).

I suspected as much. Thanks for confirming :D

Just be aware that the value of the 'captured' local will be the value when the lambda is invoked, not declared.
e.g.

Code:

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Dim I As Integer = 0
Dim o = Sub()
                Dim K As Integer = I
          End Sub
I = 1
o()        'K within the lambda will be assigned 1, not 0

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