Scanning a .cs file or a directory

Question

This is a console application which takes as an argument either a .cs file or a directory. If it's a .cs file, it scans it; if it's a directory, it scans all .cs files within the directory.

A simplified view of a method which chooses whether it's a file or a directory and reports errors is this one:

public static void ProcessPath(string path)
{
    if (path.EndsWith(".cs"))
    {
        if (File.Exists(path))
        {
            Program.ScanFile(path);
        }
        else
        {
            Console.WriteLine("The specified file doesn't exist.");
            Environment.Exit(1);
        }
    }
    else
    {
        if (Directory.Exists(path))
        {
            Program.ScanDirectory(path);
        }
        else
        {
            if (File.Exists(path))
            {
                Console.WriteLine("The path corresponds to a file, but only *.cs files are supported.");
            }
            else
            {
                Console.WriteLine("The specified directory doesn't exist.");
            }

            Environment.Exit(1);
        }
    }
}

How can I rewrite the if/else logic in a more elegant way? Would it improve readability?

Answer 1

In my opinion, the easiest way would be to embrace exceptions. DirectoryNotFoundException and FileNotFoundException are there for a reason, and actually even calling .Exists might not save you from them - the file might be moved/removed between the Exists and the action you're taking next.

You can do:

public static void ProcessPath(string path)
{
    var extension = Path.GetExtension(path);

    if(string.IsNullOrEmpty(extension))
    {
        Program.ScanDirectory(path);
    }
    else
    {
        if(extension != ".cs")
            throw new NotSupportedException("Only .cs files are supported");

        Program.ScanFile(path);
    }
}

And either catch those exceptions higher up and write them to console or (considering you're doing Environment.Exit in your example), just let them propagate and crash the application.