Sub main visual basic ошибка

ok, I have an A level computing exam on Monday, and I have been working on the pre-release skeleton code.

This morning when I tried I got an error saying 'Sub Main' was not found. There clearly is a Sub Main() in the code which I will paste in below.

I tried adding another sub main() before getting a second error saying Sub Main() has multiple definitions.

I really need to get this sorted, so any help would be greatly appreciated.

Here is the code for the Sub Main() by itself:

 Sub Main()
    Dim Choice As Char
    Dim Deck(52) As TCard
    Dim RecentScores(NoOfRecentScores) As TRecentScore
    Randomize()
    Do
        DisplayMenu()
        Choice = GetMenuChoice()
        Select Case Choice
            Case "1"
                LoadDeck(Deck)
                ShuffleDeck(Deck)
                PlayGame(Deck, RecentScores)
            Case "2"
                LoadDeck(Deck)
                PlayGame(Deck, RecentScores)
            Case "3"
                DisplayRecentScores(RecentScores)
            Case "4"
                ResetRecentScores(RecentScores)
        End Select
    Loop Until Choice = "q"
End Sub

And here is the full code if that helps:

 'Skeleton Program code for the AQA COMP1 Summer 2014 examination
 'this code should be used in conjunction with the Preliminary Material
 'written by the AQA COMP1 Programmer Team
 'developed in the Visual Studio 2008 (Console Mode) programming environment (VB.NET)
Module CardPredict
Const NoOfRecentScores As Integer = 3
Structure TCard
    Dim Suit As Integer
    Dim Rank As Integer
End Structure
Structure TRecentScore
    Dim Name As String
    Dim Score As Integer
End Structure
Sub Main()
    Dim Choice As Char
    Dim Deck(52) As TCard
    Dim RecentScores(NoOfRecentScores) As TRecentScore
    Randomize()
    Do
        DisplayMenu()
        Choice = GetMenuChoice()
        Select Case Choice
            Case "1"
                LoadDeck(Deck)
                ShuffleDeck(Deck)
                PlayGame(Deck, RecentScores)
            Case "2"
                LoadDeck(Deck)
                PlayGame(Deck, RecentScores)
            Case "3"
                DisplayRecentScores(RecentScores)
            Case "4"
                ResetRecentScores(RecentScores)
        End Select
    Loop Until Choice = "q"
End Sub
Sub Main()
    Console.Write("Boo")
End Sub
Function GetRank(ByVal RankNo As Integer) As String
    Dim Rank As String = ""
    Select Case RankNo
        Case 1 : Rank = "Ace"
        Case 2 : Rank = "Two"
        Case 3 : Rank = "Three"
        Case 4 : Rank = "Four"
        Case 5 : Rank = "Five"
        Case 6 : Rank = "Six"
        Case 7 : Rank = "Seven"
        Case 8 : Rank = "Eight"
        Case 9 : Rank = "Nine"
        Case 10 : Rank = "Ten"
        Case 11 : Rank = "Jack"
        Case 12 : Rank = "Queen"
        Case 13 : Rank = "King"
    End Select
    Return Rank
End Function
Function GetSuit(ByVal SuitNo As Integer) As String
    Dim Suit As String = ""
    Select Case SuitNo
        Case 1 : Suit = "Clubs"
        Case 2 : Suit = "Diamonds"
        Case 3 : Suit = "Hearts"
        Case 4 : Suit = "Spades"
    End Select
    Return Suit
End Function
Sub DisplayMenu()
    Console.WriteLine()
    Console.WriteLine("MAIN MENU")
    Console.WriteLine()
    Console.WriteLine("1.  Play game (with shuffle)")
    Console.WriteLine("2.  Play game (without shuffle)")
    Console.WriteLine("3.  Display recent scores")
    Console.WriteLine("4.  Reset recent scores")
    Console.WriteLine()
    Console.Write("Select an option from the menu (or enter q to quit): ")
End Sub
Function GetMenuChoice() As Char
    Dim Choice As Char
    Choice = Console.ReadLine
    Console.WriteLine()
    Return Choice
End Function
Sub LoadDeck(ByRef Deck() As TCard)
    Dim Count As Integer
    FileOpen(1, "deck.txt", OpenMode.Input)
    Count = 1
    While Not EOF(1)
        Deck(Count).Suit = CInt(LineInput(1))
        Deck(Count).Rank = CInt(LineInput(1))
        Count = Count + 1
    End While
    FileClose(1)
End Sub
Sub ShuffleDeck(ByRef Deck() As TCard)
    Dim NoOfSwaps As Integer
    Dim Position1 As Integer
    Dim Position2 As Integer
    Dim SwapSpace As TCard
    Dim NoOfSwapsMadeSoFar As Integer
    NoOfSwaps = 1000
    For NoOfSwapsMadeSoFar = 1 To NoOfSwaps
        Position1 = Int(Rnd() * 52) + 1
        Position2 = Int(Rnd() * 52) + 1
        SwapSpace = Deck(Position1)
        Deck(Position1) = Deck(Position2)
        Deck(Position2) = SwapSpace
    Next
End Sub
Sub DisplayCard(ByVal ThisCard As TCard)
    Console.WriteLine()
    Console.WriteLine("Card is the " & GetRank(ThisCard.Rank) & " of " & GetSuit(ThisCard.Suit))
    Console.WriteLine()
End Sub
Sub GetCard(ByRef ThisCard As TCard, ByRef Deck() As TCard, ByVal NoOfCardsTurnedOver As Integer)
    Dim Count As Integer
    ThisCard = Deck(1)
    For Count = 1 To (51 - NoOfCardsTurnedOver)
        Deck(Count) = Deck(Count + 1)
    Next
    Deck(52 - NoOfCardsTurnedOver).Suit = 0
    Deck(52 - NoOfCardsTurnedOver).Rank = 0
End Sub
Function IsNextCardHigher(ByVal LastCard As TCard, ByVal NextCard As TCard) As Boolean
    Dim Higher As Boolean
    Higher = False
    If NextCard.Rank > LastCard.Rank Then
        Higher = True
    End If
    Return Higher
End Function
Function GetPlayerName() As String
    Dim PlayerName As String
    Console.WriteLine()
    Console.Write("Please enter your name: ")
    PlayerName = Console.ReadLine
    Console.WriteLine()
    Return PlayerName
End Function
Function GetChoiceFromUser() As Char
    Dim Choice As Char
    Console.Write("Do you think the next card will be higher than the last card (enter y or n)? ")
    Choice = Console.ReadLine
    Return Choice
End Function
Sub DisplayEndOfGameMessage(ByVal Score As Integer)
    Console.WriteLine()
    Console.WriteLine("GAME OVER!")
    Console.WriteLine("Your score was " & Score)
    If Score = 51 Then
        Console.WriteLine("WOW!  You completed a perfect game.")
    End If
    Console.WriteLine()
End Sub
Sub DisplayCorrectGuessMessage(ByVal Score As Integer)
    Console.WriteLine()
    Console.WriteLine("Well done!  You guessed correctly.")
    Console.WriteLine("Your score is now " & Score & ".")
    Console.WriteLine()
End Sub
Sub ResetRecentScores(ByRef RecentScores() As TRecentScore)
    Dim Count As Integer
    For Count = 1 To NoOfRecentScores
        RecentScores(Count).Name = ""
        RecentScores(Count).Score = 0
    Next
End Sub
Sub DisplayRecentScores(ByVal RecentScores() As TRecentScore)
    Dim Count As Integer
    Console.WriteLine()
    Console.WriteLine("Recent scores:")
    Console.WriteLine()
    For Count = 1 To NoOfRecentScores
        Console.WriteLine(RecentScores(Count).Name & " got a score of " & RecentScores(Count).Score)
    Next
    Console.WriteLine()
    Console.WriteLine("Press the Enter key to return to the main menu")
    Console.WriteLine()
    Console.ReadLine()
End Sub
Sub UpdateRecentScores(ByRef RecentScores() As TRecentScore, ByVal Score As Integer)
    Dim PlayerName As String
    Dim Count As Integer
    Dim FoundSpace As Boolean
    PlayerName = GetPlayerName()
    FoundSpace = False
    Count = 1
    While Not FoundSpace And Count <= NoOfRecentScores
        If RecentScores(Count).Name = "" Then
            FoundSpace = True
        Else
            Count = Count + 1
        End If
    End While
    If Not FoundSpace Then
        For Count = 1 To NoOfRecentScores - 1
            RecentScores(Count) = RecentScores(Count + 1)
        Next
        Count = NoOfRecentScores
    End If
    RecentScores(Count).Name = PlayerName
    RecentScores(Count).Score = Score
End Sub
Sub PlayGame(ByVal Deck() As TCard, ByRef RecentScores() As TRecentScore)
    Dim NoOfCardsTurnedOver As Integer
    Dim GameOver As Boolean
    Dim NextCard As TCard
    Dim LastCard As TCard
    Dim Higher As Boolean
    Dim Choice As Char
    GameOver = False
    GetCard(LastCard, Deck, 0)
    DisplayCard(LastCard)
    NoOfCardsTurnedOver = 1
    While NoOfCardsTurnedOver < 52 And Not GameOver
        GetCard(NextCard, Deck, NoOfCardsTurnedOver)
        Do
            Choice = GetChoiceFromUser()
        Loop Until Choice = "y" Or Choice = "n"
        DisplayCard(NextCard)
        NoOfCardsTurnedOver = NoOfCardsTurnedOver + 1
        Higher = IsNextCardHigher(LastCard, NextCard)
        If Higher And Choice = "y" Or Not Higher And Choice = "n" Then
            DisplayCorrectGuessMessage(NoOfCardsTurnedOver - 1)
            LastCard = NextCard
        Else
            GameOver = True
        End If
    End While
    If GameOver Then
        DisplayEndOfGameMessage(NoOfCardsTurnedOver - 2)
        UpdateRecentScores(RecentScores, NoOfCardsTurnedOver - 2)
    Else
        DisplayEndOfGameMessage(51)
        UpdateRecentScores(RecentScores, 51)
    End If
End Sub
End Module

Thanks in advance,
Ed

It’s actually a bit more complicated, and I fear you may have learned the wrong lesson from what DB suggested, useful though it may be.

As you might expect, every program has to know where to start. No matter what you write, it ends up being a series of VERY simple instructions, because that’s all that the CPU can do. All that higher level languages do is make it easier to create complex programs, but they all end up as a series of sequential instructions. You can see them as a stack of cards. When the program begins, it takes the first card from the stack and does what is on the card, then takes the next card from the stack and so on. It’s not quite that simple, as it can keep going back to earlier places in the stack and repeating steps, or even create a second process and move a selection of the cards over to that separate process so that both are going through their stacks of cards at the same time.

However, there always has to be that first card. By long standing tradition, that is Sub Main(). For a very long time, you could ALWAYS find Sub Main(), and that would be roughly where things started (some memory could be set up ahead of time, but nothing much). The first line in Sub Main was the first card in the stack.

With Windows programming in .NET, there is ALWAYS a Sub Main….but you can’t ALWAYS find it. You used to be able to, back in .NET 2002 and 2003, but since then it could be hidden. Windows programs usually begin with a startup form, in which case you’d have a hard time finding Sub Main, if you even can.

What DB showed you is the style that Windows applications had to follow back in 2002 and 2003, and which is still used for console apps as he demonstrated. If you create a Windows application rather than a console app, then you’ll have a startup form (which is usually the first one given to you, by default, though you are free to change that), and neither the module nor the Sub Main is necessary. In that case, the code you had would be fine as you had it, but you’d also have a startup form, which would hide the Sub Main from you.

A class library is a dll. You’ve doubtless seen a few items with that extension. The key point about a dll is that it doesn’t have a Sub Main, plain or hidden. Therefore, you can’t execute a dll because there is no starting point in it. Using the stack of cards analogy, you could say that a dll is one or more stacks of cards, but none of them is the first one. That type of project holds code and objects that will be used by one or more other projects. They can’t stand alone, because they can’t start on their own. They have to be included into some project that actually has a starting point. Once included in, they can be used by that other project. Typically, you create a dll to store methods and objects that you feel you’ll be able to use in multiple projects, though there are other uses for them, as well.

So, don’t feel that you MUST have a module and a Sub Main. You must have one for a console app, but need not write either one for a Windows forms app, and can’t have a meaningful Sub Main for a class library.

It’s actually a bit more complicated, and I fear you may have learned the wrong lesson from what DB suggested, useful though it may be.

As you might expect, every program has to know where to start. No matter what you write, it ends up being a series of VERY simple instructions, because that’s all that the CPU can do. All that higher level languages do is make it easier to create complex programs, but they all end up as a series of sequential instructions. You can see them as a stack of cards. When the program begins, it takes the first card from the stack and does what is on the card, then takes the next card from the stack and so on. It’s not quite that simple, as it can keep going back to earlier places in the stack and repeating steps, or even create a second process and move a selection of the cards over to that separate process so that both are going through their stacks of cards at the same time.

However, there always has to be that first card. By long standing tradition, that is Sub Main(). For a very long time, you could ALWAYS find Sub Main(), and that would be roughly where things started (some memory could be set up ahead of time, but nothing much). The first line in Sub Main was the first card in the stack.

With Windows programming in .NET, there is ALWAYS a Sub Main….but you can’t ALWAYS find it. You used to be able to, back in .NET 2002 and 2003, but since then it could be hidden. Windows programs usually begin with a startup form, in which case you’d have a hard time finding Sub Main, if you even can.

What DB showed you is the style that Windows applications had to follow back in 2002 and 2003, and which is still used for console apps as he demonstrated. If you create a Windows application rather than a console app, then you’ll have a startup form (which is usually the first one given to you, by default, though you are free to change that), and neither the module nor the Sub Main is necessary. In that case, the code you had would be fine as you had it, but you’d also have a startup form, which would hide the Sub Main from you.

A class library is a dll. You’ve doubtless seen a few items with that extension. The key point about a dll is that it doesn’t have a Sub Main, plain or hidden. Therefore, you can’t execute a dll because there is no starting point in it. Using the stack of cards analogy, you could say that a dll is one or more stacks of cards, but none of them is the first one. That type of project holds code and objects that will be used by one or more other projects. They can’t stand alone, because they can’t start on their own. They have to be included into some project that actually has a starting point. Once included in, they can be used by that other project. Typically, you create a dll to store methods and objects that you feel you’ll be able to use in multiple projects, though there are other uses for them, as well.

So, don’t feel that you MUST have a module and a Sub Main. You must have one for a console app, but need not write either one for a Windows forms app, and can’t have a meaningful Sub Main for a class library.