[2008] n Tier, Classes and Data Access

I am working on my first n tier project and having a lot of trouble getting my head around wirining it all up. I have a customer class

VB Code:

Public Class Customer
    Inherits BOBase
    Private Const CN_CustomerCode As String = "CustomerCode"
    Private Const CN_CompanyName As String = "CompanyName"
 
    Private _CustomerCode As String
    Public Property CustomerCode() As String
        Get
            Return _CustomerCode
        End Get
        Private Set(ByVal value As String)
            _CustomerCode = value
        End Set
    End Property
    Private _CompanyName As String
    Public Property CompanyName() As String
        Get
            Return _CompanyName
        End Get
        Set(ByVal value As String)
            If _CompanyName <> value Then
                Dim propertyName As String = "CompanyName"
                Me.DataStateChanged(EntityStateEnum.Modified)
                _CompanyName = value
            End If
        End Set
    End Property
    Private Sub New()
 
    End Sub
    Public Shared Function Create(ByVal custCode As String) As Customer
        Dim cust As Customer
        Dim dt As DataTable
        dt = DAC.ExecuteDataTable("GetCustomerByCode_SP", _
            DAC.parameter(CN_CustomerCode, custCode))
 
        cust = New Customer()
        With dt.Rows(0)
            cust.CustomerCode = .Item(CN_CustomerCode).ToString
            cust.CompanyName = .Item(CN_CompanyName).ToString
        End With
        cust.DataStateChanged(EntityStateEnum.Unchanged)
        Return cust
    End Function
End Class

Just to test it out I put this is the Form Load Event

Dim myCode As String = "ABC"
Me.CustomerBindingSource1.DataSource = Customer.Create(myCode)

Nothing comes up. I don't get an error or anything. The form just loads with out anything in the fields (I have bound them all). When I set a Break Point on the Me.CustomerBindingSource it doesn't stop there either. Is there something that I am missing?

Any ideas?

Your code looks alright, how have you bound the form fields? Have you set DataMember properties on the bound fields on the form?

I have bound it like this.

http://www.liberty1st.org/images/bindings.JPG

Where do I set the Datamember properties?

I found this here but there were no options to set.

http://www.liberty1st.org/images/binding.jpg

The CustomerBinding has different names in these two screen shots but they are the same in the project.

I think I got it now. I had two issues. For some reason the form load event was not firing off when then form was loaded. Once I took care of that I started getting errors, which enabled me to track down the problem.

Next I removed the VS Designer Code for the control binding and did my own with this.

Dim aCust As Customer
aCust = Customer.Create("ABC")
txtCompany.Text = aCust.CompanyName
txtContact.Text = aCust.CustomerCode

Ok the loading of the controls is working now. So the next thing I want to do is save any changes back to the database. Since I am not using the CustomerBindingSource I need to do it in code but I am unsure of the syntax.

This is what I have so far.

VB Code:

Public Function ProcessSave() _
        As Boolean Implements MDIInterface.ProcessSave
 
        Dim success As Boolean
        Dim aCust As Customer = Nothing
        Try
            aCust.ContactName = txtContact.Text
            aCust.Notes = txtNotes.Text
            aCust.Save()
            Return success
        Catch ex As Exception
            MessageBox.Show(ex.Message & vbNewLine & ex.StackTrace)
        End Try
 
    End Function

I get this error Object reference not set to an instance of an object.

at PTWin.frmCustomer.ProcessSave() When I try to do a save.

Any ideas?