t4.cs

namespace ConsoleApplication {
  class Program
  {
    static void Main(string[] args)
    {
      List<int> things = new List<int>() { 10, 20, 31, 40 };
      // ... Find index of first odd
      int oddIndex = things.FindIndex(x => x % 2 != 0);
      Console.WriteLine(oddIndex);
    }
  }
}