C# extension method that emulate SQL's IN (...).

Extensions.cs

public static class Extensions
{
  public static bool In<T>(this T obj, params T[] others) where T : IEquatable<T>
  {
      bool res = false;
  
      for (int i = 0; i < others.Length; i++)
      {
          if (obj.Equals(others[i]))
          {
              res = true;
              break;
          }
      }
  
      return res;
  }
}

Now restricted to types which implement IEquatable