Checking Standard Input in C#

Question

I\'m writing a small command line utility whose purpose is to parse the output of another utility. I want it to be invokable in two ways:

c:\\> myutility file         


        

Answer 1

I've been using Pieter's solution for a while until I realised it doesn't work in Mono. Mono doesn't throw an exception when retrieving Console.KeyAvailable with piped input, so that approach doesn't help.

However, as of .NET 4.5, Console actually provides a new field IsInputRedirected which makes this a lot simpler, removes the obscurity and the unnecessary try/catch:

TextReader reader;

if (args.Length > 1) {
    reader = new StreamReader(new FileStream(args[1], FileMode.Open));
} else {
    if (Console.IsInputRedirected) {
        reader = Console.In;
    } else {
        Console.WriteLine("Error, need data");
        return;
    }
}

Process(reader);

Answer 2

Looks like you should be able to use some Windows API calls to determine that. Hans Passant's answer even has a helper class to wrap it all up.

Answer 3

The quick and dirty way is to wrap Console.KeyAvailable in a try/catch and if that throws, you know that input is redirected from a file. It's not very unusual to use try/catch to detect a state when you cannot find an appropriate method to do the checking for you.