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


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

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

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.

  1. Start a New project in Visual Basic. Form1 is created by default.
  2. 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_OOM = 8&
    Const SE_ERR_DLLNOTFOUND = 32&
    Const SE_ERR_SHARE = 26&
    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"
    msg = "Access denied"
    Case SE_ERR_OOM
    msg = "Out of memory"
    msg = "DLL not found"
    msg = "A sharing violation occurred"
    msg = "Incomplete or invalid file association"
    msg = "DDE Time out"
    msg = "DDE transaction failed"
    msg = "DDE busy"
    msg = "No association for file extension"
    msg = "Invalid EXE file or error in EXE image"
    Case Else
    msg = "Unknown error"
    End Select
    MsgBox msg
    End If
    End Sub
  3. 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."


"Programmer's Reference, Volume 2: Functions" of the Microsoft Windows Software Development Kit (SDK), pages 901-904

Id. de artículo: 170918 - Última revisión: 08/30/2004 - Revisión: 1