'The API Function.
Public Declare Function GetOpenFileName Lib "comdlg32.dll" _
Alias "GetOpenFileNameA" (pOpenfilename As OPENFILENAME) As Long

'Now come some Types.
Public Enum GFNFlags
OFN_ALLOWMULTISELECT = &H200
OFN_CREATEPROMPT = &H2000
OFN_EXPLORER = &H80000
OFN_FILEMUSTEXIST = &H1000
OFN_HIDEREADONLY = &H4
OFN_LONGNAMES = &H200000
OFN_NOCHANGEDIR = &H8
OFN_NODEREFERENCELINKS = &H100000
OFN_NOLONGNAMES = &H40000
OFN_NONETWORKBUTTON = &H20000
OFN_NOREADONLYRETURN = &H8000
OFN_NOTESTFILECREATE = &H10000
OFN_NOVALIDATE = &H100
OFN_OVERWRITEPROMPT = &H2
OFN_PATHMUSTEXIST = &H800
OFN_READONLY = &H1
End Enum

Type OPENFILENAME
lStructSize As Long
hwndOwner As Long
hInstance As Long
lpstrFilter As String
lpstrCustomFilter As String
nMaxCustFilter As Long
nFilterIndex As Long
lpstrFile As String
nMaxFile As Long
lpstrFileTitle As String
nMaxFileTitle As Long
lpstrInitialDir As String
lpstrTitle As String
Flags As Long
nFileOffset As Integer
nFileExtension As Integer
lpstrDefExt As String
lCustData As Long
lpfnHook As Long
lpTemplateName As String
End Type

'This is the wrapper Function.
Public Function OpenDialog(ByVal OwnerhWnd As Long, _
ByVal Filters As String, ByVal FilterIndex As Long, _
ByVal FNameLength As Long, _
Optional ByVal InitFolder As String = "", _
Optional ByVal InitFileName As String = "", _
Optional ByVal dlgTitle As String = "", _
Optional ByVal Flags As GFNFlags = 0) As String
'Dimension some variables.
Dim GFN As OPENFILENAME

'Sort out some of the Type we will pass.
GFN.lStructSize = Len(GFN)
GFN.hwndOwner = OwnerhWnd
GFN.hInstance = App.hInstance

'Sort out the filters.
For I = 1 To Len(Filters)
If Mid$(Filters, I, 1) = "|" Then
Filters = Left$(Filters, I - 1) & Chr$(0) & _
Right$(Filters, Len(Filters) - I)
End If
Next

'Finish setting up the Type.
GFN.lpstrFilter = Filters
GFN.nFilterIndex = FilterIndex
GFN.lpstrFile = InitFileName & String$(FNameLength - Len(InitFileName), Chr$(0))
GFN.nMaxFile = FNameLength
GFN.lpstrFileTitle = String$(FNameLength, Chr$(0))
GFN.nMaxFileTitle = FNameLength
GFN.lpstrInitialDir = InitFolder
GFN.lpstrTitle = dlgTitle
GFN.Flags = Flags

'Get and return the filename.
If GetOpenFileName(GFN) >= 1 Then
OpenDialog = GFN.lpstrFile
Else
OpenDialog = Chr$(0)
End If

End Function

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Visual Basic-6 has emerged as one of the standard Windows Programming Language and it has become a must for all Software people for developing Applications in Visual Environment. So it is, one must learn Visual Basic-6.

What is our Objective in this Courseware?


The Overall Objective in this Courseware is to give a Hands-on Approach to develop different projects in Visual Basic-6.0 using intrinsic, professional and user–created ActiveX controls and also develop projects using databases, DAO’s, ADO’s, DLL’s, Documents, Crystal Reports etc. covering almost all the essential features of VB-6 Professional Edition. After reading one lesson any interested reader will be able to get complete hands-on experience with the VB project and get a sense of fulfilment and achievement. Learning by doing is the motto with which this courseware is written. After giving a short introduction about VB-6 we will explain how to create and execute a project in VB using some intrinsic ActiveX controls. Creating and executing projects will be the central theme of all the lessons which we will be giving in this courseware.

What is Visual Basic-6?


Visual Basic-6 has its origin in Basic which was developed round about the year 1960, when high level languages were just being introduced to the computer community. Microsoft has made it extremely powerful by gearing all its good features to the Windows environment. Starting with the version 3 and then with 4, and then with 6, Visual Basic is now at version 6. Basic is a Procedure Oriented Language intended to implement single tasks in text based environment whereas Visual Basic is an Event Driven Language intended to implement Projects or Applications containing multiple tasks in Windows Environment.

What can Visual Basic do for you?

Visual Basic can serve as an ideal front end tool for the clients to interact. It has got connectivity mechanisms for all types of databases situated far and wide in a network and so it can cater to the needs of a large body of clients. Using the latest ActiveX technologies, it can integrate the functionalities provided by other applications like Word Excel and other Windows. Its internet capabilities provide easy access to documents and applications across the internet. Above all it embodies the Object Oriented Technology, which is the cutting edge technology for all the present day developments in the Software World. The final application is a true EXE file and so can be freely distributed.


Structure of VB-6 Projects:


We said earlier that VB-6 implements projects or applications. A project is developed using one or more Forms. A Form is simply a window containing one or more Controls. Controls in VB consist of labels, text boxes, list boxes, combo boxes, scroll bars etc. which are the constituents of windows environment. It is only the controls that give VB, its immense power and so there is a lot of interest in creating more and more powerful controls. ActiveX controls mark a significant development in controls technology. In fact all controls in VB-6 are ActiveX controls, which have the extension .ocx. These controls have properties whose values can be initialized at design time and also varied during run time. The properties are something like variables. The controls are activated by codes written in a high level language. By associating our problem variables with the properties of the controls, our problem variables can be manipulated to give the problem solution. In summary we can say that a VB project is made of forms, controls and their properties and codes.

Integrated Development Environment:

The working environment in VB is often referred to as the Integrated Development Environment or IDE, because it integrates many different functions such as design, editing, compiling and debugging within a common environment. Since all our projects are developed only in the IDE, let us now have a brief look at its features. You will be able to understand their uses at the time of building projects. The VB IDE looks as shown in the figure.