C# List.Clear() method not getting correct response-CodePudding

I am trying to map the below class to a destination class using the below code. Here trying to map Employee class to

        static void Main(string[] args)
        {
            var emp = new List<Employee>()
            {
                new Employee()
                {
                    FirstName = "Test",
                    LastName = "Performance",
                    ID="1",
                    Availabities = new List<Availability>()
                    {
                        new Availability()
                        {
                            BeginDate = DateTime.Now,
                            EndDate = DateTime.Now.AddDays(1)
                        }
                    }
                 },
                 new Employee()
                 {
                     FirstName = "Test1",
                     LastName = "Performance1",
                     ID="2",
                     Availabities = new List<Availability>()
                    {
                        new Availability()
                        {
                            BeginDate = DateTime.Now,
                            EndDate = DateTime.Now.AddDays(10)
                        }
                     }
                 },
                  new Employee()
                 {
                     FirstName = "Test123",
                     LastName = "Performance1",
                     ID="3",
                     Availabities = new List<Availability>()
                    {
                        new Availability()
                        {
                            BeginDate = DateTime.Now,
                            EndDate = DateTime.Now.AddDays(5)
                        },
                        new Availability()
                        {
                            BeginDate = DateTime.Now,
                            EndDate = DateTime.Now.AddDays(3)
                        }
                     }
                 }
            };

Here is the destination object mapping, here the Employee to be mapped with EmployeeDest.

            List<AvailabilityDest> empAvailabilitiesDest = new List<AvailabilityDest>();

            var results = new List<EmployeeDest>();

            foreach (var token in emp)
            {
                empAvailabilitiesDest.Clear();

                foreach (var item in token.Availabities)
                {
                    
                    var empAvailability = new AvailabilityDest
                    {
                        BeginDateDest = item.BeginDate,
                        EndDateDest = item.EndDate,
                    };
                        empAvailabilitiesDest.Add(empAvailability);
                }
                var employee = new EmployeeDest
                {
                    FirstNameDest = token.FirstName,
                    LastNameDest = token.LastName,
                   IDDest =token.ID,
                    AvailabitiesDest = empAvailabilitiesDest
                };
                results.Add(employee);
               
            }
            Console.WriteLine(results);
        }

Here the empAvailabilitiesDest.Clear() is not clearing the list and the availabilityDest is getting increased with each iteration.

I am missing something here .

How can I optimize the code here to get a better performance?

CodePudding user response：

Presumably the real problem here is that all your employee objects are sharing the same list; it doesn't matter whether you clear it, add things, etc: if there's one list and it is shared between all the employees, then changes to that list will show against every employee, and it will appear incorrect.

Presumably, you really just want to move the list creation to inside the foreach per employee:

var results = new List<EmployeeDest>();
foreach (var token in emp)
{
    List<AvailabilityDest> empAvailabilitiesDest = new List<AvailabilityDest>
();
    // your previous code unchanged
}

CodePudding user response：

Use Linq.

  results = emp.Select(token => new EmployeeDest
            {
                FirstNameDest = token.FirstName,
                LastNameDest = token.LastName,
                IDDest = token.ID,
                AvailabitiesDest = token.Availabities.Select(item => new AvailabilityDest
                {                        
                    BeginDateDest = item.BeginDate,
                    EndDateDest = item.EndDate,
                }).ToList()
            }).ToList();