CODEWITHSUNDEEP
vb.netanonymous-methods
Orion Edwards
Orion Edwards

Reputation: 123622

Does VB.NET have anonymous functions?

From what I can find on google, VB.NET only has one-statement lambdas, and not multi-statement anonymous functions. However, all the articles I read were talking about old versions of VB.NET, I couldn't find anything more recent than vs2008 beta 1 or 2.

So the question: How can I do this in VB.NET?

C# code:

private void HandleErrors( Action codeBlock ){
    try{
        codeBlock();
    }catch(Exception e){
        //log exception, etc
    }
}

HandleErrors(() => {
    var x = foo();
    x.DoStuff();
    etc
});

Upvotes: 16

Views: 22567

Answers (6)

Sam
Sam

Reputation: 483

It does in VB10:

Dim food = New With {
    .ID = 1,
    .Name = "Carrot",
    .Type = (
        Function(name As String)
            If String.IsNullOrEmpty(name) Then Return String.Empty

            Select Case name.ToLower()
                Case "apple", "tomato": Return "Fruit"
                Case "potato": Return "Vegetable"
            End Select

            Return "Meat"
        End Function
    )(.Name)
}
Dim type = food.Type

Or, corresponding to your code:

Sub HandleErrors(codeBlock As Action)
    Try
        codeBlock()
    Catch e As Exception
        ' log exception, etc.
    End Try
End Sub

HandleErrors(Sub()
        Dim x = foo()
        x.DoStuff()
        ' etc.
    End Sub)

Upvotes: 35

David
David

Reputation: 1

Anonymous isn't a delegate or function it's a strong dynamical type

you can use generic functions

Sub Main()
      Dim PersonDynamicType = AnonyFunc(New With {.Name = "david", .Family = "Fisher"})
      Console.Write(PersonDynamicType.Name)
End Sub

Function AnonyFunc(Of t)(v As t) As t
      Return v
End Function

Upvotes: -1

PhillGee
PhillGee

Reputation: 1

in this example I have a list of operations but only want to find one from a list (of T) where the IDs match:

Return operations.Find(Function(p) p.OperationID = operationID)

operationID is a local variable passed in to the method and operations is a generic list.

Upvotes: 0

Jason E Vetter
Jason E Vetter

Reputation: 1

This is inaccurate. VB.NET does in fact have anonymous methods. Here is an example:

Private Function JsonToObject(Of T)(Value As String) As T
    Dim JavaScriptSerializer As New System.Web.Script.Serialization.JavaScriptSerializer()
    Return JavaScriptSerializer.Deserialize(Of T)(Value)
End Function

Dim People As Generic.List(Of Person) = JsonToObject(Of Generic.List(Of Person))(Json)

Upvotes: -5

Denis Troller
Denis Troller

Reputation: 7501

Visual Basic .NET has only lambda expressions.

It does not support 'anonymous delegates" in the current version, though it will (and on multiple lines at that) in VS2010.

Right now the only option is to declare your method somewhere and pass it with the Addressof operator.

Upvotes: 18

Dustin Campbell
Dustin Campbell

Reputation: 9855

VB9 has only single-line anonymous functions. We're adding full statement and multi-line lambdas in VB10.

Upvotes: 9

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