How to access controls and variables, across Class and Code-behind? - asp.net

Question

i have ASP.NET page, its code-behind, and a Class file:
Folder1/page.aspx (asp.net page), it contains a label:
<asp:Label runat="server" ID="Label1" Visible="false"></asp:Label>
Folder1/page.aspx.vb (code-behind), it calls connection.vb like this:
Dim x As New Connection
Protected Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles button1.Click
x.checkusernameExists(TextBoxUsername.Text)
' I try to access `Boolean variable` Flag from Class file but I can't.
End Sub
App_Code/connection.vb (a class file that i created):
Public Class Connection
Public Sub checkusernameExists(ByVal username1 As String)
Dim flag as Boolean
' I try to access here `Label1.text` & `Label1.visible` to work on it but I can't.
End Sub
End Class
My Questions
1 - How can I access the Label1 from the ASP.NET page in Connection.vb?
2 - How can I access the Boolean variable from Connection.vb in page.aspx.vb (code behind)?
I am really stuck in this.
Thank you.

Answer 1

Use (public) properties or method parameters.
You have to ask yourself following: why should a class that is responsible for a connection(i assume to database) have access to your GUI at all? Don't hardlink different layers with each other, otherwise you won't be able to use them alone.
I would suggest to let the connection class do it's work and that is not to modify your frontend. Instead the controller (the aspx page) should manage it's GUI and call the connection class, using the return value to determine what to do next with the Label.
So return a Boolean to indicate if the user is valid:
Public Class Connection
Public Shared Function checkusernameExists(ByVal username1 As String)As Boolean
Dim userExists As Boolean
' acces db to check if the username exists '
Return userExists
End Sub
End Class
in your page:
Protected Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles button1.Click
Dim userExists As Boolean = Connection.checkusernameExists(TextBoxUsername.Text)
Label1.Visible = userExists
If Label1.Visible Then Label1.Text = "Hello again " & TextBoxUsername.Text
End Sub

Answer 2

make flag as property and set this property in checkusernameExists function
Public Class Connection
Public Property Flag as Boolean
Public Sub checkusernameExists(ByVal username1 As String)
// set flag here
Flag = True // or whateever value returned from the database
' I try to access here `Label1.text` & `Label1.visible` to work on it but I can't.
End Sub
End Class
and access this instance level property in page.aspx.vb file
Dim x As New Connection
Protected Sub button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles button1.Click
x.checkusernameExists(TextBoxUsername.Text)
Label1.Visible= x.Flag;
' I try to access `Boolean variable` Flag from Class file but I can't.
End Sub

Answer 3

You can use Function to return value and pass label as parameter.
Public Function SaveChanges(ByRef Label1 As Label, ByVal username1 As String) As Boolean
{
Return True
}
It would be better if you pass the label properties to function instead of passing the object of label as it couple up two classes.