How can I define array into array in a class VB.NET

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1.89/5 (3 votes)

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Hi guys.
When I define an array into an array into a class, I give exception.
Any kindly help please?

What I have tried:

The code:

VB.NET

Class MainWindow
    Sub New()
        InitializeComponent()
        Dim MyTest(1) As Employe = New Employee()
        MyTest(1).ID = 1
        MyTest(1).Name = "John"
        MyTest(1).BankNames(1)="ISQE Bank"   '<--- The exception is in this line 
    End Sub
    Public Class Employee
        Public Property ID As Long
        Public Property Name As String
        Public Property BankNames() as String
    End Class
End Class

Posted 3-Jul-23 9:11am

Sh.H.

Updated 3-Jul-23 18:13pm

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Ralf Meier 3-Jul-23 15:40pm

and what size has this Array "BankNames" inside your Class ?
What are you trying to achieve ?

Sh.H. 3-Jul-23 16:03pm

Guess it is 10. I forgot to assign it in the main program.

4 solutions

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Richard MacCutchan · Accepted Answer · 2023-07-03T09:43:00

Well this is the sma question you already posted at Why I can't make array as class? Vb.net[^], and you were already given the answer.

However, it probably bears repeating. First issue is that you cannot set a complete array to reference a single item. When you create the array you must initialise every element within it. Also remember, as @Ralf_Meier pointed out in the previous question, that in VB.NET when declaring an array, the number in parentheses is the upper limit of the array, not the number of elements.
So ...

VB

    Sub New()
        InitializeComponent()
'        Dim MyTest(1) As Employe = New Employee() <-- this is incorrect
        Dim MtTest(1) As Employee ' that is, create an array of TWO elements
        MyTest(0) = New Employee() ' initialise the first element
        MyTest(1) = New Employee() ' initialise the second element
' only now can you access the elements MyTest(0) and MyTest(1)
        MyTest(1).ID = 1
        MyTest(1).Name = "John"
        MyTest(1).BankNames(1)="ISQE Bank"   '<--- The exception is in this line 
    End Sub

Ralf Meier · Accepted Answer · 2023-07-03T09:46:00

Solution 3

perhaps you try it like this :

VB.NET

Public Class Employee
    Public Property ID As Long
    Public Property Name As String
    Property BankNames As String()
        Get
            Return myBankNames
        End Get
        Set(value As String())
            myBankNames = value
        End Set
    End Property
    Private myBankNames(10) As String
End Class

in this case your Sub-Array has a Size of 11 Elements (0 .. 10)

After seeing the other Answers: I would prefer the Suggestion from Dave - in my opinion that would be the best approach ...

Posted 3-Jul-23 9:46am

Ralf Meier

Updated 3-Jul-23 9:54am

v2

Comments

Sh.H. 3-Jul-23 15:57pm

Thanks. But what is the different? You wrote the old version of Property in class!

Ralf Meier 3-Jul-23 16:00pm

the difference is that the class now has a defined array in it which will be delivered with the Property. Using a Porperty like a public Variable isn't a good style at any time. It's allways better to use the Getter and the Setter Methodes of it ...

Richard MacCutchan 3-Jul-23 15:57pm

I agree, but your answer is still better than mine.

Sh.H. 3-Jul-23 15:58pm

You set it to 10! I do not need to set it in class. I need to set it in main program.

Ralf Meier 3-Jul-23 16:03pm

that isn't possible - sorry.
In this case you should think about the suggestion of Dave - but that isn't an Array - that is an empty suitcase which could be filled with your need. Perhaps you engage yourself a little with that ...

Sh.H. 4-Jul-23 0:08am

I tested all solutions. Only this one worked. Thanks.
I am going to write a clean version under all posts.

Ralf Meier 4-Jul-23 2:58am

the Solution from Dave should also work if you use it in the right way. But a List is different to an Array - that is something you should realize ...

Dave Kreskowiak · Accepted Answer · 2023-07-03T09:43:00

You never said what the exception was, but I can take a guess.

In your Employee class, you declared a property called BankNames that CAN hold an array of strings. You did not actually DEFINE the array of strings. BankNames doesn't point to an array yet.

A better way to do it would be to use a List(Of String) instead of an array.

VB.NET

Class MainWindow
    Sub New()
        InitializeComponent()

        Dim MyTest(1) As Employee = New Employee()
        MyTest(0).ID = 1
        MyTest(0).Name = "John"
        MyTest(0).BankNames.Add("ISQE Bank")
    End Sub
End Class

Public Class Employee
    Public Property ID As Long
    Public Property Name As String
    Public Property BankNames As New List(Of String)
End Class

Sh.H. · Accepted Answer · 2023-07-03T18:13:00

Solution 4

Thanks everybody. As Ralf Meier says, I write a clean code here as final solution.
the only thing should be change is the place of parenthesis in the class. It should be after String, not after BankNames. :-)

VB.NET

Class MainWindow
    Sub New()
        InitializeComponent()
        Dim MyTest(1) As Employe = New Employee()
        MyTest(1).ID = 1
        MyTest(1).Name = "John"
        Dim MyTest(1).BankNames(1) As string  '<--- Here makes an array of BankNames with size of 2.
        MyTest(1).BankNames(1)="ISQE Bank"   
    End Sub
    Public Class Employee
        Public Property ID As Long
        Public Property Name As String
        Public Property BankNames as String()
    End Class
End Class

Posted 3-Jul-23 18:13pm

Sh.H.

Updated 3-Jul-23 18:16pm

v4

Comments

Ralf Meier 4-Jul-23 3:00am

I#M sorry - you version may work ... but it isn't a good way to realize that. I don't agree with it ...

Sh.H. 4-Jul-23 5:33am

@Ralf Meier
Why? Please explain your reason.

Ralf Meier 4-Jul-23 5:43am

In my opinion the memory-usage comes from the underlying class. In your Solution your dimension of the BankNames-Array is done outside it.
What happens if you later (in same months or more) go back to your application ? Or someone complete different ? I suppose that is difficult to realize the/your layout. Also in my opinion it is complete against OOP - but that are my 2 cents ...

Sh.H. 4-Jul-23 7:40am

Thanks. Hope someone find better solution.

Ralf Meier 4-Jul-23 12:18pm

I don't believe ... For your issue the best approach would be, as allready mentioned by me, the Solution with the List (of String).
Perhaps you take a look on in and engage yourself with it ...

Sh.H. 4-Jul-23 17:56pm

Here is problem by using List(Of String). I have used Redim in my project. Becuause numbers of the array continuesly added up, and I use Ubound() to have the boundaries of it. But I don't know how can I have them with List (Of String).

Ralf Meier 4-Jul-23 18:33pm

List is a Class-Object with own Methods and Properties.
One of it's Methodes is "Add" - with that you enter a new Entry into the List. Also you have other Methods like "Remove" and so on.
It's Property "Count" delivers you the Number of Entries inside the List.
As I allready pointed out : you should engage yourself with that - List is a very mighty Tool ...

Sh.H. 5-Jul-23 1:40am

Yes I understand you. What I mean is I to use List (Of String), I have to reprogram a lot of codes in the project. And this is very hard for now.

Ralf Meier 5-Jul-23 2:37am

In Germany we say "ohne Fleiss kein Preis" which means "without working on it you have no success".
Thats your decission - I and everyone else here could only make suggestions ...

Sh.H. 7-Jul-23 23:26pm

Thanks for suggestions to you and everybody.
I will try to upgrade to List(of ) in next version. :-)

How can I define array into array in a class VB.NET

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