Equivalent of "where" command prompt command in C#

I don't think there is a built-in method in the Common Language Runtime to do this for you, but you can certainly do it yourself:

• Get the value of the PATH environment variable
• Split it on ; delimiters to get a list of directories in the path
• Check each of those directories to see if it contains program

Example:

public static string FindInPath(string filename)
{
    var path = Environment.GetEnvironmentVariable("PATH");
    var directories = path.Split(';');

    foreach (var dir in directories)
    {
        var fullpath = Path.Combine(dir, filename);
        if (File.Exists(fullpath)) return fullpath;
    }

    // filename does not exist in path
    return null;
}

Don't forget to add .exe to the filename. (Or, you could modify the code above to search for any executable extension: .bat, .com, .exe; or perhaps even any extension at all.)