Microsoft KB Archive/170918

= How To Use ShellExecute to Launch Associated File (32-bit) =

Article ID: 170918

Article Last Modified on 8/30/2004

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APPLIES TO


 * Microsoft Visual Basic 6.0 Learning Edition
 * Microsoft Visual Basic 6.0 Professional Edition
 * Microsoft Visual Basic 6.0 Enterprise Edition
 * Microsoft Visual Basic 5.0 Control Creation Edition
 * Microsoft Visual Basic 5.0 Learning Edition
 * Microsoft Visual Basic 5.0 Professional Edition
 * Microsoft Visual Basic 5.0 Enterprise Edition
 * Microsoft Visual Basic 4.0 Standard Edition
 * Microsoft Visual Basic 4.0 Professional Edition
 * Microsoft Visual Basic 4.0 32-Bit Enterprise Edition

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This article was previously published under Q170918



SUMMARY
You can use the Windows API ShellExecute function to start the application associated with a given document extension without knowing the name of the associated application. For example, you could start the Paintbrush program by passing the filename ARCADE.BMP to the ShellExecute function.



MORE INFORMATION
The ShellExecute function opens or prints the specified file. Following is the declaration to use when calling this function from Visual Basic:

Declare Function ShellExecute Lib "shell32.dll" Alias "ShellExecuteA" _ (ByVal hwnd As Long, ByVal lpszOp As String, _                   ByVal lpszFile As String, ByVal lpszParams As String, _                    ByVal LpszDir As String, ByVal FsShowCmd As Long) _ As Long

The following table provides descriptions for each parameter:

Parameter    Description

hwnd         Identifies the parent window. This window receives any message boxes an application produces (for example, for error             reporting).

lpszOp       Points to a null-terminated string specifying the operation to perform. This string can be "open" or "print." If this parameter is NULL, "open" is the default value.

lpszFile     Points to a null-terminated string specifying the file to open.

lpszParams   Points to a null-terminated string specifying parameters passed to the application when the lpszFile parameter specifies an executable file. If lpszFile points to a string specifying a document file, this parameter is NULL.

LpszDir      Points to a null-terminated string specifying the default directory.

FsShowCmd    Specifies whether the application window is to be shown when the application is opened.

Step-by-Step Example
The following example demonstrates how to start an application or load a document into its associated application. The Windows API ShellExecute function is different from the Visual Basic Shell function in that you can pass the ShellExecute function the name of a document and it will launch the associated application, and then pass the filename to the application.

 Start a New project in Visual Basic. Form1 is created by default.  Add the following code to the General Declarations section of Form1:

Option Explicit

Private Declare Function ShellExecute Lib "shell32.dll" Alias _ "ShellExecuteA" (ByVal hwnd As Long, ByVal lpszOp As _     String, ByVal lpszFile As String, ByVal lpszParams As String, _      ByVal lpszDir As String, ByVal FsShowCmd As Long) As Long

Private Declare Function GetDesktopWindow Lib "user32" As Long

Const SW_SHOWNORMAL = 1

Const SE_ERR_FNF = 2& Const SE_ERR_PNF = 3& Const SE_ERR_ACCESSDENIED = 5& Const SE_ERR_OOM = 8& Const SE_ERR_DLLNOTFOUND = 32& Const SE_ERR_SHARE = 26& Const SE_ERR_ASSOCINCOMPLETE = 27& Const SE_ERR_DDETIMEOUT = 28& Const SE_ERR_DDEFAIL = 29& Const SE_ERR_DDEBUSY = 30& Const SE_ERR_NOASSOC = 31& Const ERROR_BAD_FORMAT = 11&

Function StartDoc(DocName As String) As Long Dim Scr_hDC As Long Scr_hDC = GetDesktopWindow StartDoc = ShellExecute(Scr_hDC, "Open", DocName, _         "", "C:\", SW_SHOWNORMAL) End Function

Private Sub Form_Click Dim r As Long, msg As String r = StartDoc("C:\WINDOWS\ARCADE.BMP") If r <= 32 Then 'There was an error Select Case r                 Case SE_ERR_FNF msg = "File not found" Case SE_ERR_PNF msg = "Path not found" Case SE_ERR_ACCESSDENIED msg = "Access denied" Case SE_ERR_OOM msg = "Out of memory" Case SE_ERR_DLLNOTFOUND msg = "DLL not found" Case SE_ERR_SHARE msg = "A sharing violation occurred" Case SE_ERR_ASSOCINCOMPLETE msg = "Incomplete or invalid file association" Case SE_ERR_DDETIMEOUT msg = "DDE Time out" Case SE_ERR_DDEFAIL msg = "DDE transaction failed" Case SE_ERR_DDEBUSY msg = "DDE busy" Case SE_ERR_NOASSOC msg = "No association for file extension" Case ERROR_BAD_FORMAT msg = "Invalid EXE file or error in EXE image" Case Else msg = "Unknown error" End Select MsgBox msg End If     End Sub  Run the project and click the form.

General Information About the Process
If the function succeeds, the return value is the instance handle of the application that was run. If there was an error, the return value is less than or equal to 32.

The file specified by the lpszFile parameter can be a document file or an executable file. If it is a document file, this function opens or prints it depending on the value of the lpszOp parameter. If it is an executable file, this function opens it even if the lpszOp specifies "PRINT."

