c# - Why OrderByDescending not recognized as build method

Question

private static void findNewestFile(List<string> list)
{
    foreach (string dir in list)
    {
        var directory = new DirectoryInfo(dir);
        var file = directory.GetFiles("*.doc").OrderByDescending(f => f.LastWriteTime).First();
    }
}

This function received list of folders I try to find the newest file from each directory but the method OrderByDescending not recognized and the compiler error is:

Error 1 'System.Array' does not contain a definition for 'OrderByDescending' and no extension method 'OrderByDescending' accepting a first argument of type 'System.Array' could be found (are you missing a using directive or an assembly reference?)

Answer 1

Most probably you are missing using System.Linq