Arrays

[Jeremy Martin]

Hi,

I have a class like this

Public Class UserInfo
    Public UserName As String
    Public Password As String
    Public Premissions As String
    Public FirstName As String
    Public LastName As String
    Public Comment As String
End Class

What I would like to do is have an array made of this class on my form.

example.
Dim A() As New UserInfo
A(0).UserName = "ME"
A(1).UserName = "You"
...

I find my problem being that I can not use the keyword New with an array. And if I don't use the keyword New, it doesn't work with this error message: Object reference not set to an instance of an object.


Any help would be appreciated.

Jeremy

[Edneeis]

You have to call new on the individual elements of the array before you use them or assign them all in the delcaration:

'either
Dim A() As UserInfo
A(0)=New User()
A(0).UserName = "ME"
A(1)=New User()
A(1).UserName = "You"
 
'or
Dim A() As New UserInfo={New User(), New User(), New User()}
A(0).UserName = "ME"
A(1).UserName = "You"

Or if you want to add a constructor to the class:

Public Class UserInfo
    Public UserName As String
    Public Password As String
    Public Premissions As String
    Public FirstName As String
    Public LastName As String
    Public Comment As String
 
 Public Sub New()
    mybase.New()
 End Sub
 
 Public Sub New(username as string)
    Me.UserName=username
 End Sub
 
End Class
 
Dim A() As New UserInfo={New User("Me"), New User("You"), New User("Them")}

[Lethal]

Edneeis, You seem to have picked up .NET very well. I need to start cracking on learning .NET more. What books did u read?

Thanks

[Edneeis]

Really the only book I have used is 'Programming Visual Basic.NET' by Francesco Balena it is the Core Reference book and covers quite a lot of info.
I also have 'Advanced Remoting in VB.NET' but that only covers the Remoting topic. Also all the examples carry over from one another and I'm a skip around guy so that kind of bugs me. I prefer more reference style books like the first one mentioned.
Also since everything is object based it makes things easier to learn you just go to the namespace you need and poke around a bit.

[Jeremy Martin]

See my problem is that when I type: Dim A() As New UserInfo
it says: arrays cannot be declared with 'New'

any ideas?

Jeremy

[hellswraith]

You are trying to declare and initialize an unknown value. You just can't do that. When you use the new keyword, you are actually creating it in memory. When you do this:
Dim A() As New UserInfo
The compiler has no idea how many instances of UserInfo to create in memory.

Here is what I would do:

        Dim i As Integer

        'First declare your array.
        Dim A(5) As UserInfo

        'Now you need to initialize all the objects of the array.
        'This will actually create them in memory.
        For i = 0 To 4
            A(i) = New UserInfo()
        Next

        A(0).UserName = "ME"
        A(1).UserName = "You"

        MessageBox.Show(A(1).UserName.ToString())

[Edneeis]

Sorry I cut and pasted and forgot to remove the NEW keyword in the first example. I'll correct it.