using System;

using System.Collections.Generic;

using System.Linq.Expressions;

using System.Reflection;

public class Program

{

    public static void Main()

    {

        List<string> dates = new List<string>();

​

        // locate the methods to be called

        MethodInfo add = dates

            .GetType()

            .GetMethod(

                "Add",

                new Type[] { typeof(string) });

​

        MethodInfo toString = typeof(DateTime)

            .GetMethod(

                "ToString",

                new Type[] { typeof(string) });

​

        // ParameterExpression is used to map a value from the caller

        // to the lambda body

​

        // this is the same for object instances as well as method

        // parameters

        ParameterExpression list = Expression.Parameter(

            dates.GetType());

​

        ParameterExpression date = Expression.Parameter(

            typeof(DateTime));

​

        // use Expression.Constant to convert a 'normal' value into an expression

        ConstantExpression format = Expression.Constant(

            "MMM d");

​

        MethodCallExpression toStringCall = Expression.Call(

            date,

            toString,

            new Expression[] { format });

​

        // define the body of the lambda

​

        // we're passing in the body of one method call in as a

        // parameter to another method call

        MethodCallExpression body = Expression.Call(

            list,

            add,

            new Expression[] { toStringCall });

​

        Expression<Action<List<string>, DateTime>> lambda = Expression.Lambda<Action<List<string>, DateTime>>(

            // this is going to be the function body/logic

​

            // the value returned from a function is the last expression in its body

            body,

​

            // this is the parameter list being passed in to the lambda body

​

            // have to use same ParameterExpression instances referenced in

            // expression body definition above to get them to map through Func call

            new ParameterExpression[] { list, date });

​

        // create the Action from the lambda

        Action<List<string>, DateTime> action = lambda.Compile();

​

        // use Action to execute method

        // this will format the date using the specified format

        // and add the formatted string to the list

        action(dates, DateTime.Parse("1/1/2020"));

        action(dates, DateTime.Parse("1/2/2020"));

        action(dates, DateTime.Parse("2/1/2020"));

​

        string datesAsString = string.Join(",", dates);

​

        Console.WriteLine(datesAsString);

    }

}