Collections and updated Class properties

[trials_54]

I have a CarCollection that inherits CollectionBase. I add the items in a Car Class to a combobox and to the Collection. I have a MakeCurrent button that makes the selectedindex in the combobox the current Car. When I run a method in the application that increases the Mileage (among other things) on the Current Car in the Collection the values(like MIleage) do not update. Only the last item in the combobox list will update.

[jmcilhinney]

If you bind your collection to the ComboBox then that won't be an issue. Don't have two versions of the data: one for the ComboBox and one for the collection. Have one version of the data for the collection and then bind that to the control. The whole point of data-binding is that changes to the backing data are propagated to the control and vice versa.

Create your CarCollection and bind it to a BindingSource, then bind the BindingSource to your ComboBox. Now to add a new Car to the collection you call the AddNew method of the BindingSource to update both the collection and the ComboBox. To get the selected Car you can use the ComboBox's SelectedItem property or the BindingSource's Current property. They will both return a reference to the same object, which you can then update. The object they refer to is in the bound collection, so it too is updated and everyone's happy.

[trials_54]

Thank you for your reply. I am not using a Data source. I believe that binding would apply in a situation where I was using a Data source. Am i right?

[jmcilhinney]

Data-binding applies to any situation where you want to bind data to controls. You can bind all sorts of data. The DataSource property of a control accepts any object that implements the IList or IListSource interface. The most common data source are DataTables and BindingSources, but arrays and collections are just as valid. You assign your CarCollection object to the DataSource property of a BindingSource or control just as you can bind a DataTable.

[Pickles89]

Jm, I tried what you suggested to trials_54 with an example of my own.

After filling a collection 'Products' with objects 'Product',
and adding this collection as the datasource to the bindingsource, then binding a combobox to the bindingsource, I get the following in my combobox

[122,clsproducts.product]
[123,clsproducts.product]
[124,clsproducts.product]

How do you set the displaymember and valuemember as properties of the 'Product'

ps Did try combobox1.displaymember="ProductCode"

[jmcilhinney]

Jm, I tried what you suggested to trials_54 with an example of my own.

After filling a collection 'Products' with objects 'Product',
and adding this collection as the datasource to the bindingsource, then binding a combobox to the bindingsource, I get the following in my combobox

[122,clsproducts.product]
[123,clsproducts.product]
[124,clsproducts.product]

How do you set the displaymember and valuemember as properties of the 'Product'

ps Did try combobox1.displaymember="ProductCode"

If you have bound a collection of Product objects to a ComboBox and set the DisplayMember to "ProductCode" then your ComboBox will display a string representation of the ProductCode property of each item. Firstly, does the Product class have a ProductCode property? Check the spelling and note that the DisplayMember property is case-sensitive.

[Pickles89]

Yes It does.

Product Class

  

    Private _ProductID As Integer
    Private _ProductCode As String
    Private _ProductDesc As String

 Public Property ProductID() As Integer
        Get
            Return _ProductID
        End Get
        Set(ByVal value As Integer)
            _ProductID = value
        End Set
    End Property

    Public Property ProductCode() As String
        Get
            Return _ProductCode
        End Get
        Set(ByVal value As String)
            _ProductCode = value
        End Set
    End Property

    Public Property ProductDescription() As String
        Get
            Return _ProductDesc
        End Get
        Set(ByVal value As String)
            _ProductDesc = value
        End Set
    End Property

Testing

    Private myB As New BindingSource
    Private myprods As New clsProducts.products

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

         myprods.GetProducts(13, False)  'Retrieves records via sql to fill a generic.dictionay collection
         myB.DataSource = myprods

        ComboBox1.DisplayMember = "ProductCode"
        ComboBox1.DataSource = myB

[jmcilhinney]

That would suggest to me that that's what that property is returning.

[Pickles89]

Was going to post a small full example. Then I twigged.

myB.DataSource=myprods.VALUES

[trials_54]

Here is the binding I have done:
txtVIN.Text = MyCarCollection.Item(cboCars.SelectedIndex).VIN.ToString
txtMileage.Text = MyCarCollection.Item(cboCars.SelectedIndex).Mileage.ToString
txtGasLevel.Text = MyCarCollection.Item(cboCars.SelectedIndex).GasLevel.ToString
txtMaxGasLevel.Text = MyCarCollection.Item(cboCars.SelectedIndex).MaxGasLevel.ToString
txtOilLevel.Text = MyCarCollection.Item(cboCars.SelectedIndex).Oil.ToString
cboCars.Refresh()

[jmcilhinney]

Was going to post a small full example. Then I twigged.

myB.DataSource=myprods.VALUES

I take it then that your collection class is a custom Dictionary.

[trials_54]

Sorry. I don't know the term "custom dictionary". The CarCollection inherits CollectionBase.

[jmcilhinney]

Here is the binding I have done:
txtVIN.Text = MyCarCollection.Item(cboCars.SelectedIndex).VIN.ToString
txtMileage.Text = MyCarCollection.Item(cboCars.SelectedIndex).Mileage.ToString
txtGasLevel.Text = MyCarCollection.Item(cboCars.SelectedIndex).GasLevel.ToString
txtMaxGasLevel.Text = MyCarCollection.Item(cboCars.SelectedIndex).MaxGasLevel.ToString
txtOilLevel.Text = MyCarCollection.Item(cboCars.SelectedIndex).Oil.ToString
cboCars.Refresh()

That's not binding. That's just assigning a bunch of values to your TextBoxes. If it was binding you wouldn't have to do any of that. First you should bind your CarCollection to the ComboBox, e.g.

cboCars.DisplayMember = "Name"
cboCars.ValueMember = "ID"
cboDataSource = myCarCollection

Now you bind the other properties to the TextBoxes, e.g.

txtVIN.DataBindings.Add("Text", myCarCollection, "VIN")
txtMileage.DataBindings.Add("Text", myCarCollection, "Mileage")

and so on for each TextBox. Now when you select a car in the ComboBox all TextBoxes will update automatically. Also, if you edit a value in a TextBox the corresponding item in the collection will be updated automatically. That's what data-binding means: the UI and backing data store are bound so a change to one also affects the other.

[trials_54]

i'm sorry but I don't know what "Display Member" and "Value Member" refer to.

[trials_54]

I believe that your method is way more efficient however this project is for a Class in OOP in am taking and we haven't covered Data Bindings yet and I think I should stick to using what I know.

[jmcilhinney]

I believe that your method is way more efficient however this project is for a Class in OOP in am taking and we haven't covered Data Bindings yet and I think I should stick to using what I know.

Okeydokey then. In that case then you should get the selected car only once:

Dim selectedCar As Car = myCarCollection(cboCars.SelectedIndex)

Now you can get or set the properties of 'selectedCar'.

[trials_54]

I don't see how this will get the values of VIN and Mileage, etc. into the textboxes.

[VBDT]

how do you change the values of the car. Show the method.

[trials_54]

just the constuctor in the Car Class

[VBDT]

just the constuctor in the Car Class

Ok, now I am confused. What is the problem you are having? In your first post the problem was that even though you assigned new values to the car properties, they didn’t change. That means that the object is already created so how you change the properties in the constructor?

[trials_54]

Well, the Drive method takes the current values for Mileage and GasLevel from the Car that is selected and changes the values by adding miles and reducing gas consumption.

[VBDT]

Ok show the Drive method!!!

[jmcilhinney]

Let's look at the VIN property only for the moment. Your car class should look something like this:

Public Class Car
 
    Private _vin As String
 
    Public Property Vin() As String
        Get
            Return Me._vin
        End Get
        Set(ByVal value As String)
            Me._vin = value
        End Set
    End Property
 
End Class

You would create a Car object something like this:

Dim myCar As New Car
 
myCar.Vin = "ABC123"

If you want to declare a constructor that takes property values you can:

Public Sub New(ByVal vin As String)
    Me._vin = vin
End Sub

In that case you could create a Car object like this:

Dim myCar As New Car("ABC123")

Now in your application, if you want to forgo data binding then you can add the contents of a CarCollection to a ComboBox:

For Each myCar As Car In myCarCollection
    Me.ComboBox1.Items.Add(myCar.ToString)
Next myCar

You'd have to change the ToString part to the name of the property you wanted to display. Now you would handle all the property chnages like so:

Private myCarCollection As New CarCollection
Private selectedCar As Car
 
Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, _
                                           ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
    If Me.ComboBox1.SelectedIndex = -1 Then
        Me.selectedCar = Nothing
        Me.TextBox1.Clear()
    Else
        Me.selectedCar = Me.myCarCollection(Me.ComboBox1.SelectedIndex)
        Me.TextBox1.Text = Me.selectedCar.Vin
    End If
End Sub
 
Private Sub TextBox1_Validated(ByVal sender As Object, ByVal e As System.EventArgs) Handles TextBox1.Validated
    If Not Me.selectedCar Is Nothing Then
        Me.selectedCar.Vin = Me.TextBox1.Text
    End If
End Sub

[trials_54]

Thanks. I already have everything you wrote(almost exactly) except the last part with the SelectedIndexChanged and Validating. When I add code like yours to Validating it tells me the VIN is read only (which it how I coded it and the only way into it is the Sub New Constructor.

[jmcilhinney]

Well if you don't want to change the VIN then don't try to set the VIN property. Just apply the principle to the properties that you DO want to change. You should set the ReadOnly property of any TextBoxes that will contain the values of ReadOnly properties.

[trials_54]

I am suppose to use a MakeCurrent button to select the VIN from the ComboBox which will make the Car associated with that VIN current and I am not too familiar with SelectedIndexChanged. So I added the code you suggested for SelectedIndexChanged to my MakeCurrent button and the program behaves exactly as before. When I make the last Car and VIN added(to the Collection and the ComboBox) and run the Drive method the new values pop up in the text boxes as they should. But when I select any other VIN in the list the values are never changed.

[jmcilhinney]

How are you populating the ComboBox in the first place?

[trials_54]

Private Sub collect_car_VIN() 'sub procedure to add VINs to ComboBox


If counter >= 0 Then

cboCars.Items.Add(MyCarCollection.Item(counter).VIN)
counter += 1

End If

End Sub

[jmcilhinney]

So when you do this:

Me.selectedCar = Me.myCarCollection(Me.ComboBox1.SelectedIndex)

are you then getting the properties of the 'selectedCar' variable? If so I don't see how you could be getting the wrong values. If you test the VIN property of the 'selectedCar' does it give you the value displayed in the ComboBox?

Actually, just show us the code you're using to get the properties of the Car. You should have done that in the beginning so we didn't have to draw this out inch by inch. If you're having trouble with some code then show the code.

[trials_54]

I am getting the right values initially. I can switch between the VINs in the Combo box and all the textboxes fill with the right values. But when I run the Drive method only the last VIN added will give me back the right adjusted values.

[jmcilhinney]

Then you're calling the Drive method of the wrong Car object. The 'selectedCar' variable refers to the Car that has been selected. THAT is the Car whose Drive method you should be calling, i.e. the same Car object whose properties you displayed in the TextBoxes. That's what the 'selectedCar' variable is for: to refer to the selected car.

[trials_54]

It is performing the Drive method on the wrong car. I know that. But the values in the textboxes when I run Drive reflex the Car I picked from the ComboBox. But its still running it on the wrong car. After the Drive method is run the values don't change but they should .Running the Drive method when the last Car added is selected works.

[jmcilhinney]

Show Us The Code.

[trials_54]

Sorry. I guess i don't know how to post code here in the messagbox properly.

[trials_54]

Did anyone look at my code?

[trials_54]

I see that my code didn't post. I will try again
Here is the Car Class:Public Class Car
Public Event OilGood() 'declare events
Public Event ClearMiles()
Public Event LowOil()
Public Event ClearTextbox1()
Public Event GasLow()
Public Event RemoveCar()
Public Event RefreshCurrent()


Protected blnServLight As Boolean
Protected sVIN As String 'private instance variables
Protected sOil As Single
Protected intMileage As Integer 'protected instance variables
'so derived class has access
Protected sngGasLevel As Single
Private sngMaxGasLevel As Single


Public ReadOnly Property VIN() As String 'VIN property procedure
'read only

Get 'accessor that is invoked when
'a request to retrieve the property value is made
Return Me.sVIN

End Get
End Property
Public ReadOnly Property Mileage() As Integer 'Mileage property procedure
Get
Return Me.intMileage

End Get
End Property
Public Property GasLevel() As Single 'GasLevel property procedure
Get

Return Me.sngGasLevel 'return value like a function

End Get
Set(ByVal Value As Single)
Me.sngGasLevel = Value

If Value < 0 Then 'check for proper value
MessageBox.Show("Please enter a positive value for Gas Level!" _
& ControlChars.CrLf & "Gas level is below '0'", "Negative Gas Level!", _
MessageBoxButtons.OK, MessageBoxIcon.Exclamation)


RaiseEvent ClearTextbox1() 'event raised

ElseIf Value >= 0 And Value < 2 Then 'conditional clause

RaiseEvent GasLow() 'event raised

' Me.sngGasLevel = Value

ElseIf Value > Me.MaxGasLevel Then

MessageBox.Show("Tank is overfilled! Exceeded Max" & _
" " & "gas level!", "Too much gas!", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)

RaiseEvent ClearTextbox1() 'event raised

Else

Me.sngGasLevel = Value 'assings Value parameter to
'private instance variable
End If

End Set
End Property
Public Property MaxGasLevel() As Single 'MaxGasLevel property procedure
Get

Return Me.sngMaxGasLevel

End Get
Set(ByVal Value As Single)

Me.sngMaxGasLevel = Value

End Set
End Property

Public ReadOnly Property Oil() As Single
'read only property procedure
Get
Return Me.sOil

End Get
End Property
Public Overridable ReadOnly Property ServiceLight() As Boolean
Get 'property procedure
Return blnServLight

End Get
End Property
Sub New(ByVal VIN_Num As String, ByVal Mileage_Go As Integer, _
ByVal service As Boolean, ByRef count As Integer)

'Constructor

Me.sVIN = VIN_Num 'assign parameters passed to Get of Property
'procedures
Me.intMileage = Mileage_Go

End Sub
Public Overridable Function Drive(ByVal decMiles As Decimal) As Boolean
'Drive Class Method
'Overriable

If decMiles >= 0 Then
MessageBox.Show("The current mileage on the car has been increased " & _
ControlChars.CrLf & "by the amount you entered in the textbox and " & _
ControlChars.CrLf & "the gas level has been decrease by 10% of the " & _
ControlChars.CrLf & "total mileage. To see these changes reflected please " & _
ControlChars.CrLf & " click on the Display button.")

Me.intMileage += CInt(decMiles)

Me.GasLevel -= CSng((0.1 * Mileage))
RaiseEvent RefreshCurrent()

Else
Dim bCheck As Boolean
bCheck = True

Throw New NegativeAmountDrivenException(decMiles, bCheck)

End If

End Function
Public Overridable Sub PumpGas(ByVal sngNumGal As Single) 'Class Method
If Me.GasLevel < 0 Then 'checks for proper value entered

MessageBox.Show("You need to add gas ", "No Gas in tank! ", _
MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
ElseIf Me.GasLevel > Me.MaxGasLevel Then
MessageBox.Show("Too much gas in tank!", "Overmax!", MessageBoxButtons.OK, _
MessageBoxIcon.Exclamation)
Else
If sngNumGal >= 0 Then
Me.GasLevel += sngNumGal 'computation using parameter passed
Else
Throw New AmountPumpedNegativeException(sngNumGal)
End If

End If

End Sub

Public Overridable Sub DisplayPropValues(ByVal ReceiveTxt As String, _
ByVal counter As Integer, ByVal ReceiveMile As String, _
ByVal MakeCurrentRun As Boolean, ByVal ReceivedGasLev As String, _
ByVal ReceiveMaxGas As String, ByVal ReceiveOil As String)

'Class method overridable
Dim bValue As Boolean
' Dim counter As Integer
If Not MakeCurrentRun Then

If MessageBox.Show("VIN number is: " & Me.VIN & _
ControlChars.CrLf & "Mileage is: " & Me.Mileage _
& " Miles" & ControlChars.CrLf & "Gas Level is: " & _
FormatNumber(Me.GasLevel) & " Gallons" & ControlChars.CrLf & _
"Max Gas Level is: " & FormatNumber(Me.MaxGasLevel) & " Gallons" & ControlChars.CrLf & _
"Oil level is: " & Me.sOil & " Quarts" & ControlChars.CrLf & _
"Do you want to create a new Car?", "New Car?", MessageBoxButtons.YesNo, _
MessageBoxIcon.Question) = DialogResult.Yes Then


Dim mycar As Car 'new instance of Car Class
mycar = New Car(sVIN, intMileage, bValue, counter)


RaiseEvent ClearTextbox1() 'event raised
Else
RaiseEvent ClearMiles()

End If
Else
If MessageBox.Show("VIN number is: " & ReceiveTxt & _
ControlChars.CrLf & "Mileage is: " & ReceiveMile _
& " Miles" & ControlChars.CrLf & "Gas Level is: " & _
ReceivedGasLev & " Gallons" & ControlChars.CrLf & _
"Max Gas Level is: " & ReceiveMaxGas & " Gallons" & ControlChars.CrLf & _
"Oil level is: " & Me.sOil & " Quarts" & ControlChars.CrLf & _
"Do you want to create a new Car?", "New Car?", MessageBoxButtons.YesNo, _
MessageBoxIcon.Question) = DialogResult.Yes Then

Dim mycar As Car 'new instance of Car Class
mycar = New Car(sVIN, intMileage, bValue, counter)

RaiseEvent ClearTextbox1() 'event raised
Else
RaiseEvent ClearMiles()

End If

End If
End Sub

Public Sub Check_Oil(ByVal sngOilLev As Single) 'Class method


sOil = sngOilLev 'parameter assigned to private instance
'variable
If Me.sOil <= 2 Then

RaiseEvent LowOil() 'event raised
Else
RaiseEvent OilGood() 'event raised

End If
End Sub

Public Sub Add_Oil(ByVal sngOil As Single) 'Class method to
'assign parameter to read only property using private instance
'variable

sOil = sngOil

End Sub
Public Overridable Sub Unique_VIN(ByVal vin_unique() As String, _
ByVal vin As String, ByVal intcount As Integer, ByVal intcount2 As Integer) 'ByRef vin_unique() As String, _
'overridable sub that tests for duplicate VINs (will not work for Old Car
'VIN duplicate check.. just serves so MyBetterCar overrided method works)

If intcount2 > 1 Then 'tests for number of times Click Event
'that creates Better Car has been run

Do While intcount > 0 'do.. while loop to test for
'duplicate VINs

intcount -= 1

If vin_unique(intcount) = vin Then

intcount -= 1

Throw New NonUniqueVINException(vin) 'exception throw

End If
Loop
End If
End Sub

End Class

[trials_54]

Here is the BetterCar Class:
Imports System.Text.RegularExpressions 'imports class


Public Class BetterCar
Inherits Car 'inherits Base class Car

Dim NewValidate As Validate 'delclare Validate class
' protected blnServLight As Boolean 'private instance variable
Public Event NeedService() 'declare events
Public Event ClearTextbox()
Public Event ClearMiles1()
Public Event RefreshCurrent2()



Const intBase As Integer = 5000 'constant variables
Const intBaseUp As Integer = 10000


Public Overrides ReadOnly Property ServiceLight() As Boolean


Get 'property procedure
Return blnServLight

End Get
End Property
Public Overrides Function Drive(ByVal decMiles As Decimal) As Boolean

'Drive method from Car Class
'overidden
Dim strFirst As String
If decMiles >= 0 Then

MessageBox.Show("The current mileage on the car has been increased by: " & _
FormatNumber(decMiles, 0) & " Miles." & ControlChars.CrLf & _
"The gas level has been decrease by 1% of the total mileage." _
& ControlChars.CrLf & "To see these changes reflected please " & _
" " & "click on the Display button.")


MyBase.intMileage += CInt(decMiles)

MyBase.GasLevel -= CSng((0.01 * MyBase.Mileage))

RaiseEvent RefreshCurrent2()


strFirst = MyBase.intMileage.ToString.Chars(0)

If MyBase.intMileage = intBase Then
RaiseEvent NeedService()

ElseIf MyBase.intMileage = intBase + (intBaseUp * CDbl(strFirst)) Then
'determine if mileage is in increments of 10k after 5k
RaiseEvent NeedService() 'raises event

Else

Me.Light_Off() 'calls procedure
Return True
End If


Else
Throw New NegativeAmountDrivenException(decMiles, True) 'throws exception

End If

End Function

Public Sub New(ByVal vin_num As String, ByVal mileage_go As Integer _
, ByVal service As Boolean, ByRef count As Integer) 'construtor

MyBase.New(vin_num, mileage_go, True, count) 'reference to Base Class
'sub new

End Sub


Public Sub Light() 'Class method
blnServLight = True
RaiseEvent NeedService() 'raises event

End Sub
Public Sub Light_Off() 'Class method
blnServLight = False
MessageBox.Show("You do not need a schedualed service at this time." & _
ControlChars.CrLf & "You should now see the service light is off")

End Sub
Public Sub Light_On() 'Class method

blnServLight = True

MessageBox.Show("You should now see the service light is on.", _
"Attention!", MessageBoxButtons.OK, MessageBoxIcon.Exclamation)

End Sub
Public Overrides Sub DisplayPropValues(ByVal ReceiveTxt As String, _
ByVal counter As Integer, ByVal ReceiveMile As String, _
ByVal makecurrentrun As Boolean, ByVal receivedGasLev As String, _
ByVal receiveMaxGas As String, ByVal receiveOil As String)


'Car Class method
'overriden
NewValidate = New Validate
Dim bValue As Boolean
' Dim counter As Integer
If Not makecurrentrun Then

If MessageBox.Show("VIN number is: " & Me.VIN & _
ControlChars.CrLf & "Mileage is: " & Me.Mileage _
& " Miles" & ControlChars.CrLf & "Gas Level is: " & _
FormatNumber(Me.GasLevel) & " Gallons" & ControlChars.CrLf & _
"Max Gas Level is: " & FormatNumber(Me.MaxGasLevel) & " Gallons" & ControlChars.CrLf & _
"Oil level is: " & Me.sOil & " Quarts" & ControlChars.CrLf & _
"Do you want to create a new Car?", "New Car?", MessageBoxButtons.YesNo, _
MessageBoxIcon.Question) = DialogResult.Yes Then



Dim MyBetterCar As BetterCar 'new instance of BetterCar Class
MyBetterCar = New BetterCar(sVIN, intMileage, bValue, counter)


RaiseEvent ClearTextbox() 'event raised

Else
RaiseEvent ClearMiles1()
End If

Else
If MessageBox.Show("VIN number is: " & ReceiveTxt & _
ControlChars.CrLf & "Mileage is: " & ReceiveMile _
& " Miles" & ControlChars.CrLf & "Gas Level is: " & _
receivedGasLev & " Gallons" & ControlChars.CrLf & _
"Max Gas Level is: " & receiveMaxGas & " Gallons" & ControlChars.CrLf & _
"Oil level is: " & receiveOil & " Quarts" & ControlChars.CrLf & _
"Do you want to create a new Car?", "New Car?", MessageBoxButtons.YesNo, _
MessageBoxIcon.Question) = DialogResult.Yes Then

Dim mycar As Car 'new instance of Car Class
mycar = New Car(sVIN, intMileage, bValue, counter)

RaiseEvent ClearTextbox() 'event raised
Else

RaiseEvent ClearMiles1()

End If

End If

End Sub
Public Overrides Sub PumpGas(ByVal sngNumGal As Single)
If Me.GasLevel < 0 Then 'checks for proper value entered

MessageBox.Show("You need to add gas ", "No Gas in tank! ", _
MessageBoxButtons.OK, MessageBoxIcon.Exclamation)
ElseIf Me.GasLevel > Me.MaxGasLevel Then
MessageBox.Show("Too much gas in tank!", "Overmax!", MessageBoxButtons.OK, _
MessageBoxIcon.Exclamation)
Else
If sngNumGal >= 0 Then
Me.GasLevel += sngNumGal 'computation using parameter passed
Else
Throw New AmountPumpedNegativeException(sngNumGal) 'throws exception
End If

End If
End Sub
Public Overrides Sub Unique_VIN(ByVal vin_unique() As String, _
ByVal vin As String, ByVal intcount As Integer, ByVal intcount2 As Integer)

If intcount2 > 1 Then 'tests for number of times Click Event
'that creates Better Car has been run

Do While intcount > 0 'do.. while loop to test for
'duplicate VINs

intcount -= 1

If vin_unique(intcount) = vin Then

intcount -= 1

Throw New NonUniqueVINException(vin) 'exception throw

End If
Loop
End If

End Sub


End Class

[trials_54]

Here is the first part of the Form Class Inherits System.Windows.Forms.Form
Dim WithEvents NewValidate As Validate 'declares NewValidate
'object as Validate type

Public Event ClearTextbox1() 'event declaration
'declare variable to hold first VIN
Dim strVINunique() As String
Dim intCount As Integer = 0 'index of array
Dim intCount2 As Integer = 0
'declares counter that increments
'everytime the form in opened
Dim counter As Integer = 0
Dim WithEvents MyCar As Car 'declares MyCar object
Dim WithEvents MyBetterCar As BetterCar 'declares MyBetterCar object
Dim WithEvents MyCarCollection As CarCollection
Public SendTxt As String
Public SendMile As String
Public MakeCurrentRun As Boolean
Public SendGasLev As String
Public SendMaxGas As String
Public SendOil As String
Private selectedCar As Car'This program uses the BetterCar Class object which is a derived Class
'of the Car Class to use the Property Values and Methods of the Base
'Class again in the Derived Class. Overrides Drive method of the Car
'Class to change the percentage of Gas used corresponding to Mileage
'It also has some user defined Exception Classes that handle runtime
'errors not handled by the System Exceptions.Program adds new Cars and
'BetterCars to Collection. Collection class inherits CollectionBase.VINs
'are added to ComboBox. MakeCurrent button on form selects VIN form list in
'ComboBox and brings up property valules for the Car associated with VIN.
'Delete Car button availabel. Checks for duplicate VINs

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCreateBetterCar.Click
NewValidate = New Validate 'declare instance of Class object
' Dim intCount As Integer

Dim strVIN As String 'declare variable for VIN
strVIN = txtVIN.Text'assign textbox text property to
'VIN variable

intCount += 1 'index for array incremented
intCount2 += 1 'count for button click event
'incremented

'validity check
If NewValidate.ValidateData(txtMileage, "Mileage") Then

If NewValidate.ValidateData(txtGasLevel, "Gas Level") Then

If NewValidate.ValidateData(txtMaxGasLevel, "Max Gas Level") Then
If NewValidate.ValidateData(txtOilLevel, "Oil Level") Then

End If
End If
End If
End If

Dim bValue As Boolean
'variable declarations
Dim intMileage As Integer
Dim sngOil_Lev As Single

Try

Try 'try... catch to
'catch invalid cast exception and display messagebox

' Form1.ActiveForm.ResetText()

intMileage = CInt(txtMileage.Text)


sngOil_Lev = CSng(txtOilLevel.Text)
bValue = False 'set value of boolean variable

'declare
'instance of the BetterCar Class with parameters
Try
MyBetterCar = New BetterCar(strVIN, intMileage, bValue, counter)

ReDim Preserve strVINunique(intCount) 'redimension
'array so there is no limit on how many values it can
'hold; also preserve values already held

strVINunique(intCount) = strVIN 'assign VIN variable
'to array


Finally 'execute the following statements
'no matter whether exception is throw or not
MyBetterCar.Add_Oil(sngOil_Lev)


MyBetterCar.MaxGasLevel = CSng(txtMaxGasLevel.Text) 'assign
'textbox text property to Class property
MyBetterCar.GasLevel() = CSng(txtGasLevel.Text)

End Try


Catch esystem As NullReferenceException 'catch system exception and
'display message to user
MessageBox.Show("We are unable to create your New Car due to the " & _
"problem with the VIN number you entered. Sorry.")

End Try

Catch eSystem As InvalidCastException 'catch if user enters
'wrong types of values in textboxes
MessageBox.Show("You must enter a numeric value above zero" _
& ControlChars.CrLf & " in all fields.")

End Try
Try
If (MyCarCollection Is Nothing) Then
Try ' 'try.. catch

' MyBetterCar.Unique_VIN(strVINunique, strVIN, intCount, intCount2)
'call to Inherited Class to test for duplicate VINs

MyCarCollection = New CarCollection

Catch esystem As NullReferenceException 'catch system exception
MessageBox.Show("Car does not exist!")

End Try

End If

Dim message As String = ""

MyCarCollection.Add(MyBetterCar, intCount, intCount2, strVIN, message) 'add MyBetterCar object to Collection
If intCount <= 10 Then
MessageBox.Show("This is the " & message & " car you have added.")
End If


Me.collect_car_VIN()
Catch err As InvalidVINexception 'catch user defined exception
MessageBox.Show(err.Message) 'show error message stored in
'constuctor()
Catch err As InvalidVINPatternException 'catch user defined
'exception
MessageBox.Show(err.Message)
' Catch err As NonUniqueVINException 'catch user defined exception
Me.ClearText()

Catch err As NonUniqueVINException 'catch user defined
'exception
MessageBox.Show(err.Message) 'show error message
Me.ClearText()

Catch esystem As NullReferenceException 'catch system exception
MessageBox.Show("Please enter a VIN number that conforms to all of the " & _
ControlChars.CrLf & "requirements. Thank you.")

End Try

End Sub
Public Sub myBetterCar_NeedService() Handles MyBetterCar.NeedService
'event handler for NeedService event
Dim result As DialogResult

If MessageBox.Show("You are now at: " & FormatNumber(MyBetterCar.Mileage, 0) & _
" Miles" & ControlChars.CrLf & "Please service your car! You already did?" _
& ControlChars.CrLf & "Then click 'Yes' .If you haven't yet, please answer 'No'.", _
" Need Service!", MessageBoxButtons.YesNo, MessageBoxIcon.Question) _
= Windows.Forms.DialogResult.Yes Then
Me.ServLightOff()

MyBetterCar.Light_Off()

ElseIf result = Windows.Forms.DialogResult.No Then

Me.ServLightOn()

MyBetterCar.Light_On()

End If

End Sub

Private Sub btnDrive_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDrive.Click
Dim intMiles As Integer

Try 'try.. catch
intMiles = CInt(txtMiles.Text)

Try
If MyBetterCar.Drive(intMiles) = True Then
'call to Class method which
'is overridden
Me.ServLightOff()

End If

Catch err As NegativeAmountDrivenException 'catch user defined
'exception
MessageBox.Show(err.Message & "The source of the problem is: " & _
err.Source)
Dim bCheck As Boolean = True

If bCheck = True Then Me.ClearText()

End Try

Catch ex As InvalidCastException 'catch system exception

MessageBox.Show("You must enter values into all the textboxes and " & _
ControlChars.CrLf & "click the 'Create' button before using this control")

End Try

End Sub

[jmcilhinney]

That's far too much code. Post the relevant code only, and inside VBCODE tags. Post the part where you get the properties of the selected car, call its Drive method and then set its properties.

[trials_54]

Form Class cont.Private Sub btnExit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnExit.Click

If MessageBox.Show("Are you sure you want to exit?", "Exit?", _
MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.Yes Then
MyCar = Nothing 'manually clear garbage
MyBetterCar = Nothing

Me.Close() 'closes program at user request
Else
Me.Focus() 'call to procedure
txtVIN.Focus()
End If

End Sub

Private Sub btnOldDrive_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOldDrive.Click
Dim intMiles As Integer

Try
intMiles = CInt(txtMiles.Text)
MyCar.Drive(intMiles) 'call to Base Class method

Catch err As NegativeAmountDrivenException
MessageBox.Show(err.Message & "The source of the problem is: " & _
err.Source)

Dim bCheck As Boolean = True


If bCheck = True Then Me.ClearText()

Catch ex As InvalidCastException 'catch system exception

MessageBox.Show("You must enter values into all the textboxes and " & _
ControlChars.CrLf & "click the 'Create' button before using this control")

End Try

End Sub
Public Sub ClearText() 'sub procedure to clear textboxes
Dim ctlcontrol As Control
For Each ctlcontrol In Me.Controls

If TypeOf ctlcontrol Is TextBox Then
With ctlcontrol

.Text = ""
.Focus()
End With
End If

Next

End Sub

Private Sub btnClearText_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClearText.Click
Me.ClearText()

End Sub
Public Sub MyBetterCar_ClearTextboxes() Handles MyBetterCar.ClearTextbox
Dim ctlcontrol As Control 'Event handler
For Each ctlcontrol In Me.Controls

If TypeOf ctlcontrol Is TextBox Then
With ctlcontrol

.Text = ""
.Focus()
End With
End If

Next
End Sub
Public Sub MyCar_ClearTextboxes() Handles MyCar.ClearTextbox1
Dim ctlcontrol As Control 'Event handler
For Each ctlcontrol In Me.Controls

If TypeOf ctlcontrol Is TextBox Then
With ctlcontrol

.Text = ""
.Focus()
End With
End If

Next
End Sub
Private Sub MyCar_ClearMiles() Handles MyCar.ClearMiles
'event handler
Me.txtMiles.Clear()

End Sub
Private Sub MyBetterCar_ClearMiles1() Handles MyBetterCar.ClearMiles1
'event handler
Me.txtMiles.Clear()

End Sub

Private Sub btnDisplay_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDisplayBetter.Click
' Dim sendtxt As String

Try

MyBetterCar.DisplayPropValues(SendTxt, counter, SendMile, _
MakeCurrentRun, SendGasLev, SendMaxGas, SendOil)

'call to Derived Class method(overidden)


Catch eSystem As NullReferenceException 'catch system exception and message
MessageBox.Show("Please enter a numeric value greater than zero in all textboxes and" & _
ControlChars.CrLf & "be sure you clicked the 'Create Better .. button" & _
ControlChars.CrLf & " before pressing this 'Display Better... button" & _
ControlChars.CrLf & "and you did not hit the 'Create Standard... button first.")

End Try
End Sub

Private Sub btnCheckOil_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnCheckOilStandard.Click


Dim OilLevel As Single
Try 'try.. catch
OilLevel = CSng(txtOilLevel.Text)
MyCar.Check_Oil(OilLevel) 'call to Class method


Catch eSystem As InvalidCastException
MessageBox.Show("You must enter values in all the textboxes and " _
& ControlChars.CrLf & "click the 'Create' button before using this control")

End Try
End Sub
Public Sub MyBetterCar_LowOil() Handles MyBetterCar.LowOil 'Event handler

MessageBox.Show("Your oil level is low!" & ControlChars.CrLf & _
"You need to add more oil", "Low Oil", MessageBoxButtons.OK, _
MessageBoxIcon.Warning)

Me.ClearText()

End Sub
Public Sub MyBetterCar_OilGood() Handles MyBetterCar.OilGood 'Event handler

MessageBox.Show("Your oil level is OK.", "Level Good", _
MessageBoxButtons.OK, MessageBoxIcon.Information)
Me.ClearText()

End Sub
Public Sub MyCar_LowOil() Handles MyCar.LowOil 'Event handler

MessageBox.Show("Your oil level is low!" & ControlChars.CrLf & _
"You need to add more oil", "Low Oil", MessageBoxButtons.OK, _
MessageBoxIcon.Warning)
Me.ClearText()

End Sub
Public Sub MyCar_OilGood() Handles MyCar.OilGood 'Event handler

MessageBox.Show("Your oil level is OK.", "Level Good", _
MessageBoxButtons.OK, MessageBoxIcon.Information)
Me.ClearText()

End Sub