Microsoft KB Archive/147807

= How To Use ShellExecute to Launch Associated File (16-bit) =

Article ID: 147807

Article Last Modified on 7/13/2004

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APPLIES TO


 * Microsoft Visual Basic 4.0 Professional Edition
 * Microsoft Visual Basic 4.0 16-bit Enterprise Edition
 * Microsoft Visual Basic 3.0 Professional Edition
 * Microsoft Visual Basic 3.0 Professional Edition

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This article was previously published under Q147807



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 "SHELL" (ByVal hwnd%, ByVal lpszOp$, _  ByVal lpszFile$, ByVal lpszParams$, ByVal lpszDir$, ByVal _   fsShowCmd%) As Integer

The table below 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. This parameter can be one of the values described in the API ShowWindow.

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. In the following code sample, the underscore character, "_", indicates a continuation of one line of code and must be removed for Visual Basic 3.0:

 Start a New Project in Visual Basic. Form1 is created by default.  Add the following code to the general declarations section of Form1: (NOTE: Remove the keyword "PRIVATE" when using Visual Basic 3.0) Option Explicit

Const SW_SHOWNORMAL = 1

Private Declare Function ShellExecute Lib "shell.dll" (ByVal hwnd%, _     ByVal lpszOp$, ByVal lpszFile$, ByVal spszParams$, ByVal _      lpszDir$, ByVal fsShowCmd%) As Integer

Private Declare Function GetDesktopWindow Lib "USER" As Integer

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

Sub Form_Click Dim r As Integer r = StartDoc("C:\WINDOWS\ARCADE.BMP") End Sub 

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 can only open it and the lpszOp$ parameter must specify "OPEN."

