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Specifying an Application Error Code

While a vast majority of your Main() methods will return void as the return value, the ability to

return an int from Main() keeps C# consistent with other C-based languages. By convention,

returning the value 0 indicates the program has terminated successfully, while another value (such

as -1) represents an error condition (do be aware that the value 0 is automatically returned, even if

you construct a Main() method prototyped to return void).

On the Windows operating system, an application’s return value is stored within a system envi-

ronment variable named %ERRORLEVEL%. If you were to create an application that programmatically

launches another executable (a topic examined in Chapter 17), you can obtain the value of

%ERRORLEVEL% using the static System.Diagnostics.Process.ExitCode property.

Given that an application’s return value is passed to the system at the time the application ter-

minates, it is obviously not possible for an application to obtain and display its final error code

while running. However, to illustrate how to view this error level upon program termination, begin

by updating the Main() method as follows: