How To Use a Common Dialog File Open Dialog with the Win32

Article ID: Q154079
Creation Date: 29-JUL-1996
Revision Date: 31-JUL-1996

The information in this article applies to:

Standard, Professional, and Enterprise Editions of Microsoft Visual Basic, 32-bit only, for Windows, version 4.0

SUMMARY

This article provides a code sample and demonstrates how to use the File Open dialog box in the Comdlg32.dll. Making use of Comdlg32.OCX is a good reuse of resources under Windows, as Windows always has its dependent file, Comdlg32.dll, loaded. It provides an easy-to-use interface, but can be a performance hit. If you use the OCX control, you have to load the module into memory and also distribute a 90K OCX control to users of your software. To improve performance, you should minimize the use of controls in your applications. Instead, you can use the Win32 API calls directly.

If you use the API calls, you may lose some of the functionality that comdlg32.ocx offers, such as the Help button. If you require the Help button, you will need to use the comdlg32.ocx control.

MORE INFORMATION

Step by Step Example

Start a new project in Visual Basic. Form1 is created by default.

Place a Command Button on Form1.

Add the following code to the Form1 code window:
Option Explicit

Private Declare Function GetOpenFileName Lib "comdlg32.dll" Alias _ "GetOpenFileNameA" (pOpenfilename As OPENFILENAME) As Long

Private 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

Private Sub Command1_Click() Dim OpenFile As OPENFILENAME Dim lReturn As Long Dim sFilter As String OpenFile.lStructSize = Len(OpenFile) OpenFile.hwndOwner = Form1.hWnd OpenFile.hInstance = App.hInstance sFilter = "Batch Files (*.bat)" & Chr(0) & "*.BAT" & Chr(0) OpenFile.lpstrFilter = sFilter OpenFile.nFilterIndex = 1 OpenFile.lpstrFile = String(257, 0) OpenFile.nMaxFile = Len(OpenFile.lpstrFile) - 1 OpenFile.lpstrFileTitle = OpenFile.lpstrFile OpenFile.nMaxFileTitle = OpenFile.nMaxFile OpenFile.lpstrInitialDir = "C:\" OpenFile.lpstrTitle = "Use the Comdlg API not the OCX" OpenFile.flags = 0 lReturn = GetOpenFileName(OpenFile) If lReturn = 0 Then MsgBox "The User pressed the Cancel Button" Else MsgBox "The user Chose " & Trim(OpenFile.lpstrFile) End If End Sub
Press the F5 key to run the project, and click the Command button. You should see the File Open dialog appear with the options set.

REFERENCES

The Win32 SDK documents other calls to the Comdlg32.dll such as ChooseColor, ChooseFont, and GetSaveFileName.

For more information, please see the following articles in the Microsoft Knowledge Base:

   ARTICLE ID: Q106682
   TITLE     : Default Extension Ignores File Type in VB Common Dialog

   ARTICLE ID: Q137194
   TITLE     : GetOpenFileName nMaxFile Interpreted Incorrectly

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