using System;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        bool isRetry = false;

        string errorCodeMatched = string.Empty;

        string errorDescription = string.Empty;

        string errorCodeList = "Illegal_Argument";

        string[] errorCodeLists = errorCodeList.Split('|');

        List<Error> errors = new List<Error>

        {

            new Error {Code = "Illegal", Description = "Description1"},

            new Error {Code = "Illegal_Code", Description = "Description2"},

            new Error {Code = "Illegal_Value", Description = "Description3"}

        };

        errors.ForEach(error => {

            if (errorCodeList.ToUpper().Contains(error.Code.ToUpper())) // This will return true because "Illegal_Argument" contains "Illegal"

            //if (!string.IsNullOrEmpty(Array.Find(errorCodeLists, e => e.ToUpper().Equals(error.Code.ToUpper())))) // This will return false because it exactly matches values errorCodeLists 

            {

                isRetry = true;

                errorCodeMatched = error.Code;

                errorDescription = error.Description;

            }

        });

        Console.WriteLine(isRetry + " - " +  errorCodeMatched + " : " + errorDescription);

    }

}

​

public class Error

{

    public string Code {get; set;}

    public string Description {get; set;}

}