Visual-Basic

Visual Basic Connection to MySQL

I want to use MySQL with Visual Basic in an effort to bypass the difficulties encountered when trying to use the Microsoft database tools.  Those problems include chronic difficulties getting my distribution packages to work on customer computers.

Download zip archive of vb project that connects to MySQL database

Making a Visual Basic Installation package including MySQL

By Fudgy McFarlen, ago

VB Visual Basic ModBus Checksum Routine

Function CRC16_BIN(ByRef ModBus_Data() As Long, NumBytes As Integer) As Long
  
    Dim Temp As Long
    Dim CRC As Long
    Dim Polynomial As Long
    Dim i As Integer
    Dim j As Integer
'—– following are read sequence checksum verification vectors  — test where either hi or lo byte == 0
'— Example temperature= 1 :   1  3  64  0  1  217  144
'—         temperature=255:   1  3  64  0  255  88  16
'—         temperature=256:   1  3  64  1  0  25  192
'—         temperature=257:   1  3  64  1  1  216  0
'—                     =0 :   1  3  64  0  0  24  80
  '— verified write string = Chr(1) & Chr(6) & Chr(64) & Chr(3) & Chr(232) & Chr(24) & Chr(34)
    CRC = 65535          '–bottom 16 bits are all 1's
    Polynomial = 40961   '–poly = A001
    For i = 0 To NumBytes – 1
      CRC = CRC Xor ModBus_Data(i)
      For j = 0 To 7
        If (CRC And 1) Then
          CRC = (ShiftRight(CRC) Xor 40961)
        Else
          CRC = ShiftRight(CRC)
        End If
      Next j
    Next i
    CRC16_BIN = CRC And 65535
   
    End Function

 

Research Links

By Fudgy McFarlen, ago

Visual Basic: Returning an array from a function

How to return an array from a function

Parent Form Function that passes back an Array / Vector

 Private Sub ReceiveArray_Click()
    Dim intRcvArray() As Integer
    Dim i As Integer

    UserInterface.Text = ""
    intRcvArray = NumberList()                   ' —Get the array of strings.
   
    For i = LBound(intRcvArray) To UBound(intRcvArray)     ' —Display the strings.
       UserInterface.Text = UserInterface.Text & CStr(i) & " "
    Next i

End Sub

Private Function NumberList() As Integer()          ' — This function returns an array 
  Dim intArray() As Integer
  Dim i As Integer

    ReDim intArray(1 To 10)
    For i = 1 To 10
        intArray(i) = i             
    Next i

    NumberList = intArray
End Function

Code here: ReturnArray.zip

By Fudgy McFarlen, ago

Visual Basic: How to pass an array parameter to another routine

This routine will pass a parameter to another routine This routine receives the call with array as parameter

 

Sub TestPassArray()

  Dim LongArray(1 To 5) As Long
  Dim i As Integer
 
  For i = 1 To 5
    LongArray(i) = i
  Next i
  
  UserDisplay.Text = CStr(PassTest(LongArray()))

End Sub                                                                                                      

 

Function PassTest(ByRef LongPass() As Long) As Long

  Dim i  As Integer
  Dim Sum As Long
 
  For i = 1 To 5
     Sum = Sum + LongPass(i)
  Next i
 
PassTest = Sum
  
End Function

 

 

  1. The passing routine packs   1,2,3,4,5 into an array.
  2. The called routine calculates the sum of all the values in the array and passes the result back to the calling routine.
By Fudgy McFarlen, ago

Visual Basic: Saving Custom Control Persistant Properties

For more on this subject Google Search on VB Initproperties

You may wonder why we need the InitProperties event since the UserControl property already has an Initialize event in common with Class modules and other objects, such as forms.

The reason that we need InitProperties to initialize default values is that the Initialize event happens too often, that is, every time an instance or your control "wakes up." You only want the default property values to be assigned when the developers first sites a new copy of your control on a container. After that, you want the developer to be able to define persistent property values.

WARNING – Don't Use the Initialize Event to Set an ActiveX Control's Default Property Values : If you put code to initialize properties to their default values in your custom ActiveX control's Initialize event instead of in the InitProperties event, then you will have some very frustrated developers on your hands. Your default values will override the values the developer has assigned at design time every time the developer runs an application using your control.

—

The Property Bag is a persistent UserControl object containing the values of your control's custom, extender, and delegated properties. In fact, the Property Bag is so persistent that it doesn't get destroyed with the instances of the UserControl. This means you can store property values in the Property Bag just before an instance of the UserControl is destroyed and then retrieve the stored values when a new instance of the UserControl "wakes up" in another part of the development life cycle.

The Property Bag has two methods to store and retrieve values respectively:

  • The WriteProperty method

  • The ReadProperty method

You must know how to manipulate the Property Bag in the following situations that we discuss in the sections immediately following this one:

  • You store property values into the PropertyBag by calling its WriteProperty method in the WriteProperties event procedure.

  • You retrieve property values from the PropertyBag by calling its ReadProperty method in the ReadProperties event procedure.

  • You ensure that the WriteProperties event will fire by calling the PropertyChanged method. You'll usually do this in the Property Let procedures of your custom properties or at other appropriate places in your code where the storage value of a property changes.

—-

The operating environment fires a UserControl's ReadProperties and WriteProperties events whenever it thinks that the instantiated object's properties need to be re-initialized (ReadProperties event fires) or stored for safekeeping (WriteProperties event fires).

This arrangement makes it much easier for you, the control author, to manage these properties since you don't have to think about all the possible occasions when property values might need reading or writing. You simply need to put code for reading and writing property values in two centralized places: the ReadProperties and WriteProperties event procedures.

…………more

By Fudgy McFarlen, ago

Visual Basic PropertyBags to remember Parameters-Its in the Bag

Recalling UserControl Properties

Standard controls have properties you can set using the object browser.  The next time you bring up your VB program for editing you need to be able to recall the state of these settings.  Example #3 on this page  shows how to use a PropertyBag to remember these settings.

 

             

  BagMan PropertyBag Example

Storage to the Bag

Save to the Bag – Fill up the object to be saved to disk Stuff it in the Bag – The actual file operation to put on disk

 Private Sub cmdSave_Click()

  Dim objBag As New PropertyBag

    With objBag
        .WriteProperty "Str", "A string"
        .WriteProperty "Num", 666
        .WriteProperty "Bool", False
        .WriteProperty "Mascot", SuperBagMan.Picture

        SaveBagContents .Contents, App.Path & "\Things.bag"
    End With
   
    Set objBag = Nothing

End Sub  

                                                                                                               

Private Sub SaveBagContents(Contents As Variant, FilePath As String)

  Dim FileNum As Integer

    FileNum = FileSystem.FreeFile()

    Open FilePath For Binary As FileNum
        Put #FileNum, , Contents
    Close FileNum

End Sub

 

 

……….more

By Fudgy McFarlen, ago

How to Register an OCX File

If you are receiving errors about an ocx file, registering the file may solve the problem. To register an ocx file simply follow the simple steps below.

  • 1.Locate the file using windows explorer or My Computer. Alternatively search for the filename.
  • 2.Hold down the shift key and right click on the file. Then click 'Open With…' from the menu.
  • 3.An 'Open With' dialog box should appear. Click the button 'Other…'.
  • 4.Navigate to your windows\system32 directory and select the file 'RegSvr32.exe'. Do a file search for it if you have trouble locating the exact folder. On Windows 2000 it is typically located in c:\WINNT\System32. Click Open to select the file. Then click OK on the 'Open With' dialog.
  • 5.You should see a message indicating the file was successfully registered. If you see an error message, try restarting your computer and going through the above process again.
By Fudgy McFarlen, ago

Writing a Custom Control for Visual Basic

First Phase is always looking for example code to allow untangling very poorly written explanations.

Variable Visibility

You can pass variables / objects back and forth between a Visual Basic Form and a UserControl.  This archive has source code showing you how to do this:

     Scribble.zip 

 

You can make properties for the following things: Forms, UserControls and Class Modules. Basically any element that will behave as an object.

When to use properties?

Properties are handy when you want to generalize your code: if you're changing a setting of something, it might be better to create it as a property. Especially if you might have a need to get a return value as well. The property code can then do some additional stuff, such as switching form's menu items automatically to correct value, so you don't need to do it from whereever you set the property.

Property Passing

This accesses a property of the Custom Control

Parent Form Custom Control

 

ParentForm.Caption=UserControl1.Caption  

Dim m_Caption As String

Public Property Get Caption() As String
   Caption = m_Caption
End Property

 

……..more

By Fudgy McFarlen, ago