VB.NET handling data between different forms - vb.net

Question

I'm writing a simple application - address book. User enters new addresses and they are added as an entry to a list visible on the main form (frmStart). I use one form to add and edit (AddContForm). Add button on the frmStart works fine, however I experience some problems with the edit button as when I press it and enter new data they are added as new entry however the previous entry is still there. Logic is handled by Contact.vb class. Please let me know how to fix this problem. Here is the code:
Contact.vb
Public Class Contact
Public Contact As String
Public Title As String
Public Fname As String
Public Surname As String
Public Address As String
Private myCont As String
Public Property Cont()
Get
Return myCont
End Get
Set(ByVal value)
myCont = Value
End Set
End Property
Public Overrides Function ToString() As String
Return Me.Cont
End Function
Public Sub Display()
Dim C As New Contact
C.Cont = frmAddCont.txtTitle.Text
C.Fname = frmAddCont.txtFName.Text
C.Surname = frmAddCont.txtSName.Text
C.Address = frmAddCont.txtAddress.Text
frmStart.lstContact.Items.Add(C)
End Sub
End Class
Here is frmStart.vb
Public Class frmStart
Public Button As String
Private Sub btnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAdd.Click
Button = ""
Button = "Add"
frmAddCont.ShowDialog()
End Sub
Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDel.Click
Button = ""
Button = "Del"
Dim DelCont As Contact
DelCont = Me.lstContact.SelectedItem()
lstContact.Items.Remove(DelCont)
End Sub
Private Sub lstContact_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles lstContact.SelectedIndexChanged
End Sub
Private Sub btnEdit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEdit.Click
Button = ""
Button = "Edit"
Dim C As Contact
If lstContact.SelectedItem IsNot Nothing Then
C = DirectCast(lstContact.SelectedItem, Contact)
frmAddCont.ShowDialog()
End If
End Sub
End Class
Here is AddContFrm.vb
Public Class frmAddCont
Public Class ControlObject
Dim Title As String
Dim FName As String
Dim SName As String
Dim Address As String
Dim TelephoneNumber As Integer
Dim emailAddress As String
Dim Website As String
Dim Photograph As String
End Class
Private Sub btnConfirmAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnConfirmAdd.Click
Dim B As String
B = frmStart.Button
Dim C As New Contact
C.Display()
Me.Hide()
If B = "Edit" Then
C = DirectCast(frmStart.lstContact.SelectedItem, Contact)
frmStart.lstContact.SelectedItems.Remove(C)
End If
End Sub
Private Sub frmAddCont_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
End Sub
End Class
Update:
I really don't care much for whether the data on the AddForm is the old data or the new data. I don't understand how this code would help me achieve my goal. I think the problem now is that when I click edit previous entry on the list is not deleted (what I believe I have indicated in my question) - I tried to delete it (by using the if condition and checking what button was pressed) however it seems it is not working properly for some reason. I don't understand how your code could help me - please if possible explain it better.

Answer 1

If you're going to use the shared instance of frmAddCont, then it'll remember the data each time you show it, so you'd have to add some kind of Initialize method where you initialize all the controls to the defaults you want (for example empty textboxes).
However, the other way around it would be to do something like:
using(dlg as new frmAddCont)
{
If(dlg.ShowDialog() = DialogResult.OK)
{
Dim C As Contact = dlg.GetNewContact()
}
}
Please note, the above code is not tested and is just meant as a sample rather than the exact code you need.