Pre- and Post-execution scripts

Quite often it is desirable to perform certain actions before and/or after the script execution. Such actions can be virtually anything (copying files, executing certain applications, setting environment variables, interacting with user etc.).

CS-Script allows such actions to be specified directly in the code in a form of pre- and post-execution scripts. It means that, when composing the script (main script), you can specify any other C# script to be executed prior to or after the main script execution.
Having the pre- and post-execution actions implemented as scripts (pre- and post-scripts) gives developers a great level of flexibility. These are just some a few examples of what you can do using this approach:

dynamically compose C# scripts, which are to be imported by the main script
import COM type library, which is to be used by the main script
prepare a fresh copy of the .cs file with the implementation of the C# class for accessing the Web Service
perform some cleanup after the main script execution
log execution start and finish time of the main script
set the environment variables to be accessed from the main script

The way how pre- and post-scripts are specified in the code is similar to the one used for imported scripts or referenced assemblies:

//css_prescript file([arg0][, arg1]..[,arg2])[ignore];
//css_postscript file([arg0][, arg1]..[,arg2])[ignore];

file - script file (extension is optional)

arg0..N - script string arguments
ignore - continue execution of the main script even in case of exception in the pre-/post-script

If the string $this (or $this.name) is specified as arg0..N it will be replaced at execution time with the main script full name (or file name only).
The shorter alias directives //css_pre and //css_post can be used in place of the //css_prescript and //css_postscript respectively.

Note:
All pre- and post-scripts are executed within the same address space as the main script.

The concept of pre- and post-script is the key component of the COM and Web Service "single-line access" implementation. This functionality of the CS-Script allows to interface the Web Services and COM objects with just a single line of code. No manual steps for importing type libraries or executing the wsdl.exe are required. All can be done in the background as a pre-execution action (see Using COM and CS-Script and Web Services for details).

Remember that you may need to escape some path characters that conflict with the //css_ delimiters. See Delimiters Escaping section.

Example

This is the example of the script, which sets the environment variable greeting to "Hello!":

using System;

class Script
{
    static public void Main(string[] args)
    {
        if (args.Length > 0)
            Console.WriteLine("Setting environment variable for "+
        System.IO.Path.GetFileName(args[0])+"...");
        Environment.SetEnvironmentVariable("greeting", "Hello!");
    }
}

Now the value of the environment variable greeting is available for any script, which uses setEV.cs file as a pre-script. This is an example of such script (script.cs):

//css_prescript setEV($this);
using System;

class Script
{
    static public void Main(string[] args)
    {
        Console.WriteLine(Environment.GetEnvironmentVariable("greeting"));
    }
}

Pre- and Post-execution scripts

Example

Output

See Also