// C# Extension Method

// Doc: https://csharp-extension.com/en/method/1002247/datetime-in

​

// @nuget: Z.ExtensionMethods

​

using System;

using System.Globalization;

​

public class Program

{

    public static void Main()

    {

        DateTime date = new DateTime(2018, 12, 25);

        DateTime [] values = {new DateTime(2018, 12, 25), new DateTime(2019, 2, 28), new DateTime(2019, 2, 24), new DateTime(2017, 5, 12)};

​

        // C# Extension Method: DateTime - In

        if(date.In(values))

        {

            Console.WriteLine("{0} exists in the list.", date);

        }

        else

        {

            Console.WriteLine("{0} doesn't exists in the list.", date);

        }

    }

}