Shell

Another application can be run from a VB.NET program. Using the Shell function, we specify a target executable and any command-line arguments needed.

We learn ways to use the Shell function in practical situations. Shell() throws exceptions when files are not found, which can be handled in your program as well.

Example

To begin, we specify a target application that happens to be stored in a specific location. You can change the file name to one that exists.

Next When this program executes, the C:\procexp.exe program will be started and brought to focus on the computer.

Module Module1
    Sub Main()
        ' Run this specific executable on the shell.
        ' ... Specify that it is focused.
        Shell("C:\procexp.exe", AppWinStyle.NormalFocus)
    End Sub
End Module

Example 2

How can we use Shell to run a command-line program that performs some other action? This example uses the 7-Zip executable program, which performs compression and decompression.

Here This command line compresses all the text files on the C volume into a file called files.7z.

Return The return value is the process ID of the program that was started. Here the 7za.exe program was started as process #1296.

Module Module1
    Sub Main()
        ' Run the 7-Zip console application to compress all txt files
        ' ... in the C:\ directory.
        Dim id As Integer = Shell("C:\7za.exe a -t7z C:\files.7z C:\*.txt")
        Console.WriteLine(id)
    End Sub
End Module1296

7-Zip (A) 9.07 beta  Copyright (c) 1999-2009 Igor Pavlov  2009-08-29

[Output truncated]

Example 3

The Shell function does not work if you only pass the file name you want to open to it. Instead, you need to specify the application you want to open the file with.

Info We use Notepad to open a target text file. You could use Microsoft Word or other applications to open files.

Module Module1
    Sub Main()
        ' Use the notepad program to open this txt file.
        Shell("notepad C:\file.txt", AppWinStyle.NormalFocus)
    End Sub
End Module

Internals

The Shell function in the VB.NET language is implemented in managed code but uses lower-level constructs. It is not implemented with the Process type. The 2 types are separate.

The Shell function invokes external processes. The Process type is a more object-oriented approach. But the Shell function is still useful—it is easier to recall and use.