Textbox Line Character Limit

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Introduction

Recently, while I was working on a project, there was a need to limit the amount of text in each line of a multi line textbox to 72 characters. The challenge was to limit the text while the user is typing and to maintain the required formatting. To get this to work, I had to create a class that inherited from TextBox. In the constructor, I placed a global keyboard trap on the TextBox. When the text reaches the designated length the program will stop all keyboard characters from displaying on the screen forcing the user to hit the enter key and start a new line.

The code

In the constructor, the program calls the function HookKeyboard. In this function, the program will trap all keyboard events for the TextBox:

Public Sub New()
    MyBase.New()
    'This call is required by the Windows Form Designer.

    InitializeComponent()
    
    'Hook all Keyboard Events

    HookKeyboard(Me)
End Sub

The function isHooked in the Keyboard module, where the actual fun begins:

'This function is where you capture the key pressed. 

Public Function IsHooked(ByRef Hookstruct As KBDLLHOOKSTRUCT) As Boolean
    Dim zKey As Keys
    Dim control As Control
    Dim hInstance As Integer
    Try
        Dim ActiveWin As Integer
        'GetActiveWindow determines if the application has focus

        ActiveWin = GetActiveWindow
        
        If ActiveWin <> 0 Then
            If UBound(frmM.Lines) >= 0 Then
                If frmM.Lines(GetTextBoxCurrentLine(frmM) - 1).Length > _
                                                          MaxLengthLine Then
                'Accept Enter Button

                    If (Hookstruct.vkCode = zKey.Enter) Then
                        SendKeys.Send("{Enter}")
                        Return True
                    End If
                    'Accept BackSpace

                    If (Hookstruct.vkCode = zKey.Back) Then
                        SendKeys.Send("{BACKSPACE}")
                        Return True
                    End If
                    'Accept Up Arrow

                    If (Hookstruct.vkCode = zKey.Up) Then
                        SendKeys.Send("{UP}")
                        Return True
                    End If
                    'Accept Down Arrow

                    If (Hookstruct.vkCode = zKey.Down) Then
                        SendKeys.Send("{Down}")
                        Return True
                    End If
                    'Accept Left Arrow

                    If (Hookstruct.vkCode = zKey.Left) Then
                        SendKeys.Send("{Left}")
                        Return True
                    End If
                    'Accept Right Arrow

                    If (Hookstruct.vkCode = zKey.Right) Then
                        SendKeys.Send("{Right}")
                        Return True
                    End If
                    Return True
                End If
            End If
        End If
        Return False
    Catch ex As Exception
        MsgBox(ex.Message + vbCrLf + ex.StackTrace)
        Return False
    End Try
End Function