Reference to a non-shared member requires an object reference

[Przemek]

Hi,

I'm creating small aspnet application. The main purpose of application
is to manage list of contracts (adding, updating, deleting) and
creating reports based on database of contracts. So I've created a
class Contract, which have all contract's properties and method like
InsertContract etc. In my InsertContract method I want to pass Contract
object to my database provider class Insert method. I'm receiving an
error "Reference to a non-shared member requires an object reference".
It's understandable, because I didn't instantiate database provider
object before. I can workaround this error using "shared" keyword in my
database provider method definition. My question is, if it's correct
solution and if not, what shall I do. Here is my code:

Public Class Contract

Public Property Trademark() As String
Get
Return _trademark
End Get
Set(ByVal value As String)
_trademark = value
End Set
End Property

' other properties

Public Sub New()

End Sub

'other methods

Public Sub InsertContract ()
DatabaseProvider.InsertContract (contract)
End Sub

End Class


Public Class DatabaseProvider

Public Shared Sub InsertContract (record as Contract)

'adding contract to database

End Class

Przemek

 

[Robinson]

I'm creating small aspnet application. The main purpose of application
is to manage list of contracts (adding, updating, deleting) and
creating reports based on database of contracts. So I've created a
class Contract, which have all contract's properties and method like
InsertContract etc. In my InsertContract method I want to pass Contract
object to my database provider class Insert method. I'm receiving an
error "Reference to a non-shared member requires an object reference".
It's understandable, because I didn't instantiate database provider
object before. I can workaround this error using "shared" keyword in my
database provider method definition. My question is, if it's correct
solution and if not, what shall I do. Here is my code:

Public Class Contract

Public Property Trademark() As String
Get
Return _trademark
End Get
Set(ByVal value As String)
_trademark = value
End Set
End Property

' other properties

Several things here, mainly design issues. I would make "InsertContract" a
method on your Database provider. So you pass in a Contract object to the
provider, rather than try to make the contract itself "know" about the
provider ( ie. "myProvider.InsertContract ( myContract ). If you want to do
the latter, you need to store an reference to the provider in the contract,
which I'm sure you will agree is not quite so easy to do. You could of
course make your provider a global singleton, and then reference it with
your contract object, but I don't think that would be a very good idea.