.NET (Core and Framework)

22-Mar-11 11:09

Could the subject be any more clear?

Especially when writing your own Generic classes.
I kind of know how they work (little experience).

For example, would the following be acceptable?

Public Interface ISomething(As T)
   Function Something As T
End Interface

Public Class SomethingElse(As T)
   Public Property SomeStuff As T
   ' No explicit get/set required in .NET 4 :)
End Class

Or is that just not best practice?

I know some of the benefits, like no (un)boxing of Objects (thus fater performance and less chance on wrong casts?).
What are the drawbacks?

Edit:
And of course when to (not) use Generics Smile | :)

It's an OO world.

DaveyM6922-Mar-11 12:07

DaveyM69

22-Mar-11 12:07

Generics can be very useful. I believe the complier actually creates the classes based on the type so you end up with multiple versions of the same class - one for each (or each combination of types if using <T, V> etc). This I suppose could lead to bloat if there are lots of different Ts in your code, but there would have to be a lot! If you used object then there would only ever be one type of the class.

I'm not fond of auto properties as there is no oportunity for validation in the setter or event raising.

Dave

Binging is like googling, it just feels dirtier.
Please take your VB.NET out of our nice case sensitive forum.
Astonish us. Be exceptional. (Pete O'Hanlon)

BTW, in software, hope and pray is not a viable strategy. (Luc Pattyn)

Sander Rossel24-Mar-11 1:15

24-Mar-11 1:15

Not sure what you mean, but if you mean that the following...

Public Class Something(Of T1, T2)

   Public Function GetSomething(ByVal var As T1) As T2
      ' Get Something
   End Function

End Class

Public Class Form1

   Private _field As Something(Of SomeClass, SomeOtherClass)

   Sub Me_Load(...) Handles Me.Load
      _field = New Something(Of SomeClass, SomeOtherClass)
      Dim var As SomeOtherClass = _field.GetSomething(New SomeClass)
   End Sub

End Class

...creates a couple of versions of SomeClass and SomeOtherClass I think you are wrong.
Actually I think the only instances of SomeClass and SomeOtherClass are the Class I pass to the Function and the Class that it returns (var). And of course I have an instance of the Something(Of T1, T2) Class.
Correct me if I am wrong Smile | :)

When there is no need for validation or event raising a non-auto property creates a lot of overhead Wink | ;)

It's an OO world.

DaveyM6924-Mar-11 5:21

DaveyM69

24-Mar-11 5:21

Naerling wrote:
couple of versions of SomeClass and SomeOtherClass I
think you are wrong

I will need to check (maybe over the weekend) but I'm sure I remember reading this on MSDN or somewhere similar.

Naerling wrote:
When there is no need for validation or event raising a non-auto property
creates a lot of overhead

Not true, the backing field is created invisibly for you in the IL, these are identical to all intents and purposes (C#):

public T SomeData
{
    get; set;
}

private T someData

public T SomeData
{
    get { return someData; }
    set {someData = value; }
}

Sander Rossel24-Mar-11 5:48

24-Mar-11 5:48

With overhead I meant extra code to write and dirty your screen Laugh | :laugh:

Thanks for pointing it out though.

DaveyM69 wrote:
but I'm sure I remember reading this on MSDN or somewhere similar

I would like to read that too Smile | :)

It's an OO world.

DaveyM6926-Mar-11 6:58

DaveyM69

26-Mar-11 6:58

Here[^] it is.

Luc Pattyn26-Mar-11 7:16

Luc Pattyn

26-Mar-11 7:16

Thanks for the link. It shows even code gets instantiated!

Smile | :)

Luc Pattyn [Forum Guidelines] [My Articles] Nil Volentibus Arduum

Please use <PRE> tags for code snippets, they preserve indentation, improve readability, and make me actually look at the code.

Sander Rossel28-Mar-11 8:43

28-Mar-11 8:43

Thanks for the link!
I think I misunderstood your earlier post after reading this.
And it never actually occured to me that value and reference types would work differently (well Rob already explained it pretty well too).
This article clears some things up though.

It's an OO world.

currentElement.GetAttribute(VB.NET)

Rob Grainger25-Mar-11 5:18

Rob Grainger

25-Mar-11 5:18

If I recall correctly, the behaviour is as follows:

When the run-time loads a generic class, it does create multiple versions, but not as many as you may think.

Consider...

Public Class Pair(Of T1, T2) ' I detest the generic syntax for VB, C#'s <T1, T2> is so much clearer
    Public First As T1
    Public Second As T2
End Class

For T1, the compiler must generate a version of each value type (derived from System.Value, such as Int16, Int32, ...) because the representation of the object varies - some value types may be larger than the size of an object reference.

However, where T1 is an Object type, the variation can be omitted, as the representation remains constant.
Similarly for T2.

So for Pair(int, char) is one type, Pair(int, Person) is one, but Pair(int, object) can share the representation of Pair(int, Person). Obviously Pair(object, int) is another axis of variation, but there tend to be reasonable bounds to the amount that occur in practise.

Herboren21-Mar-11 10:10

Herboren

21-Mar-11 10:10

I am trying to retrieve a value within a textbox that has a vlue already passed to it within a webpage. As you can see I am trying to extract the last name here(red fire truck:

<span id="CallerForm1_CallerInformation1_lblLNameLabel" class="clsFormLabelSide" style="font-size:XX-Small;z-index: 109; left: 273px; position: absolute;
       top: 56px">(last)</span>
   <input name="CallerForm1:CallerInformation1:txtLName" type="text" value="RedFireTruck" maxlength="50" id="CallerForm1_CallerInformation1_txtLName" style="width:168px;z-index: 105; left: 266px; position: absolute;
       top: 72px" />

What I have been using is the chunk within the methos: Document Completed. Im trying to store its value in a variable so I can pass the var to the next screen or a different page. All I could come up with was this. keep in mind I am using a msgbox to see if anything has been saved or retrieved by so far I havent gotten any notifications:

Dim theElementCollection As HtmlElementCollection = wbCHCTrac.Document.GetElementsByTagName("input")
        If wbCHCTrac.Url.ToString.Contains("client/upd_caller.aspx?") Then
            For Each currentElement As HtmlElement In theElementCollection
                Dim controlName As String = currentElement.GetAttribute("id").ToString
                If controlName = "CallerForm1:CallerInformation1:txtLName" Then
                    MsgBox(currentElement.GetAttribute("Value").ToString)
                    
                End If
            Next
        End If

Any help would be appreciated =)

Re: currentElement.GetAttribute(VB.NET)

davidnz22-Mar-11 23:32

davidnz

22-Mar-11 23:32

I am probably stating the obvious, but I presume you have at some stage determined whether the DocumentCompleted handler is ven getting fired, and if so whether execution is ever going within the first If statement?

And am I missing something.. your html has ...

id="CallerForm1_CallerInformation1_txtLName"

but then you're looking for an id ""CallerForm1:CallerInformation1:txtLName" (colon, not underscore)

Dim controlName As String = currentElement.GetAttribute("id").ToString
If controlName = "CallerForm1:CallerInformation1:txtLName" Then

Shouldn't that be..

Dim controlName As String = currentElement.GetAttribute("id").ToString
If controlName = "CallerForm1_CallerInformation1_txtLName" Then

New SDK for visual studio projects

rodrigogroff18-Mar-11 9:39

rodrigogroff

18-Mar-11 9:39

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Not Active18-Mar-11 9:49

Not Active

18-Mar-11 9:49

Not the place for advertising.

I know the language. I've read a book. - _Madmatt

rodrigogroff18-Mar-11 9:52

rodrigogroff

18-Mar-11 9:52

This is not an add, its a free tool.

Not Active18-Mar-11 10:12

Not Active

18-Mar-11 10:12

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I know the language. I've read a book. - _Madmatt

Richard MacCutchan18-Mar-11 10:45

Richard MacCutchan

18-Mar-11 10:45

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I must get a clever new signature for 2011.

rodrigogroff18-Mar-11 11:00

rodrigogroff

18-Mar-11 11:00

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