How to pass a lambda expression as argument of a parameter in a method?

Question

Is there any way to pass a lambda expression as a parameter argument in a method? For example:

Private Sub Metodo(Expressao As ?)
    Lista = Lista.Where(Expressao)
End Sub

Answer 1

The most adopted way is to use a predefined delegate, such as the Func(Of TSource, Boolean):

Private Sub Metodo(Of TSource)(Expressao As Func(Of TSource, Boolean))
    Lista = Lista.Where(Expressao)
End Sub

The TSource is generic, if you know the specific type you can use it. If you are a Integer, can be:

Private Sub Metodo(Expressao As Func(Of Integer, Boolean))
    Lista = Lista.Where(Expressao)
End Sub

To call is not as convenient as C#:

Metodo(Function(x) x = 0)

I put in the Github for future reference.

Documentation.

Answer 2

Code:

Public Class Prj
    Public Sub Metodo(Of T)(Where As Func(Of T, Boolean))
        Lista = Lista.Where(Where)
    End Sub
End Class

How to use?

Dim c As New Prj
c.Metodo(Function(a) a = 1);

References

• How to make Parameters of VB.NET Function as Generic type?
• Generic Types in Visual Basic (Visual Basic)
• How to: Use Generic Class (Visual Basic)
• Lambda Expressions (Visual Basic)