Using lists within an if and foreach statement-CodePudding

I am creating a console application that is using user input to determine the data within two lists. Each list has the same data objects. They are name, rollNo, course and stream.

When all of the data has been inputted by the user then they are asked which stream information they would like to see. I then want to have the data that correlates with the stream input be displayed. For example if they want to see stream 1 then the information for the trainer and students on that stream should appear in the console.

This is my code below.

            Student studentOne = new Student();
            Console.WriteLine("Enter the Name of Student:");
            studentOne.name = Console.ReadLine();
            Console.WriteLine("Enter the roll number of Student:");
            studentOne.rollNo = int.Parse(Console.ReadLine());
            Console.WriteLine("Enter the course of Student:");
            studentOne.course = Console.ReadLine();
            Console.WriteLine("Enter the Stream of Student:");
            studentOne.stream = int.Parse(Console.ReadLine());

            Student studentTwo = new Student();
            Console.WriteLine("Enter the Name of Student:");
            studentTwo.name = Console.ReadLine();
            Console.WriteLine("Enter the roll number of Student:");
            studentTwo.rollNo = int.Parse(Console.ReadLine());
            Console.WriteLine("Enter the course of Student:");
            studentTwo.course = Console.ReadLine();
            Console.WriteLine("Enter the Stream of Student:");
            studentTwo.stream = int.Parse(Console.ReadLine());

            Student studentThree = new Student();
            Console.WriteLine("Enter the Name of Student:");
            studentThree.name = Console.ReadLine();
            Console.WriteLine("Enter the roll number of Student:");
            studentThree.rollNo = int.Parse(Console.ReadLine());
            Console.WriteLine("Enter the course of Student:");
            studentThree.course = Console.ReadLine();
            Console.WriteLine("Enter the Stream of Student:");
            studentThree.stream = int.Parse(Console.ReadLine());

            var studentData = new List<Student>();
            studentData.Add(studentOne);
            studentData.Add(studentTwo);
            studentData.Add(studentThree);

            Trainer trainerOne = new Trainer();
            Console.WriteLine("Enter the Name of the trainer:");
            trainerOne.name = Console.ReadLine();
            Console.WriteLine("Enter the roll number of the trainer:");
            trainerOne.trainNo = int.Parse(Console.ReadLine());
            Console.WriteLine("Enter the course of the trainer:");
            trainerOne.course = Console.ReadLine();
            Console.WriteLine("Enter the Stream of the trainer:");
            trainerOne.stream = int.Parse(Console.ReadLine());

            Trainer trainerTwo = new Trainer();
            Console.WriteLine("Enter the Name of the trainer:");
            trainerTwo.name = Console.ReadLine();
            Console.WriteLine("Enter the roll number of the trainer:");
            trainerTwo.trainNo = int.Parse(Console.ReadLine());
            Console.WriteLine("Enter the course of the trainer:");
            trainerTwo.course = Console.ReadLine();
            Console.WriteLine("Enter the Stream of the trainer:");
            trainerTwo.stream = int.Parse(Console.ReadLine());

            Trainer trainerThree = new Trainer();
            Console.WriteLine("Enter the Name of the trainer:");
            trainerThree.name = Console.ReadLine();
            Console.WriteLine("Enter the roll number of the trainer:");
            trainerThree.trainNo = int.Parse(Console.ReadLine());
            Console.WriteLine("Enter the course of the trainer:");
            trainerThree.course = Console.ReadLine();
            Console.WriteLine("Enter the Stream of the trainer:");
            trainerThree.stream = int.Parse(Console.ReadLine());

            List<Trainer> trainerData = new List<Trainer>();
            trainerData.Add(trainerOne);
            trainerData.Add(trainerTwo);
            trainerData.Add(trainerThree);

            Console.WriteLine("Which stream details do you want to view?");
            var streamInfo = int.Parse(Console.ReadLine());

            if (streamInfo == 1)
            {
                foreach (var stream in trainerData) 
                {

                }
            }

    class Student
    {
        public string name { get; set; }
        public int rollNo { get; set; }
        public string course { get; set; }
        public int stream { get; set; }
        
    }

    class Trainer
    {
        public string name { get; set; }
        public int trainNo { get; set; }
        public string course { get; set; }
        public int stream { get; set; }

    }

Any help is appreciated.

Edit: I didn't make clear what I'm asking for. I'm not sure how to have the correct data show depending on what the stream input is. I have tried using an if statement and foreach statement but I don't know if this is the best approach.

CodePudding user response：

Let's decompose the solution, let's start from reading integers:

private static int ReadInteger(string title, Func<int, bool> isValid = null) {
  if (isValid is null)
    isValid = x => true;  

  while (true) {
    if (!string.IsNullOrWhiteSpace(title))
      Console.WriteLine(title);

    if (int.TryParse(Console.ReadLine(), out int result) && isValid(result))
      return result;

    Console.WriteLine("Invalid value, please, try again.");
  }
}

private static string ReadString(string title, Func<string, bool> isValid = null) {
  if (isValid is null)
    isValid = x => true;  

  while (true) {
    if (!string.IsNullOrWhiteSpace(title))
      Console.WriteLine(title);

    string result = Console.ReadLine(); 

    if (isValid(result))
      return result;

    Console.WriteLine("Invalid value, please, try again.");
  }
}

Then we can implement ReadStudent and ReadTrainer:

public static Student ReadStudent() {
  return new Student() {
    name   = ReadString("Enter the Name of Student:", x => !string.IsNullOrWhiteSpace(x)),
    rollNo = ReadInteger("Enter the roll number of Student:", x => x >= 0),
    course = ReadString("Enter the course of Student:", x => !string.IsNullOrWhiteSpace(x)),
    stream = ReadInteger("Enter the Stream of Student:", x => x >= 0),
  };
}

public static Trainer ReadTrainer() {
  return new Trainer() {
    name   = ReadString("Enter the Name of trainer:", x => !string.IsNullOrWhiteSpace(x)),
    rollNo = ReadInteger("Enter the roll number of trainer:", x => x >= 0),
    course = ReadString("Enter the course of trainer:", x => !string.IsNullOrWhiteSpace(x)),
    stream = ReadInteger("Enter the Stream of trainer:", x => x >= 0),
  };
}

Finally, we can create as many students and trainers as we want (note for loop - what if we want to enter 100 students?):

int students = 3;
int trainers = 3;

var studentData = new List<Student>(students);

for (int i = 0; i < students;   i)
  studentData.Add(ReadStudent());

var trainerData = new List<Trainer>(trainers);

for (int i = 0; i < trainers;   i)
  trainerData.Add(ReadTrainer());

Finally, to query the list by stream you can use Linq or good old loop or Linq:

int stream = ReadInteger("Which stream details do you want to view?");

foreach (Student s in studentData)
  if (s.stream == stream)
    Console.WriteLine($"Student {s.name} Roll No {s.rollNo}");

foreach (Trainer t in trainerData)
  if (t.stream == stream)
    Console.WriteLine($"Trainer {t.name} Roll No {t.rollNo}");