add elements to object array

Question

This must be really simple but just not getting my syntax right here. let's say we have classes like two below:

class Student
{
    Subject[] subjects;
}

class Subject
{
    string Name;
    string referenceBook;
}

Here is my code:

Student univStudent = new Student();

Now, I want to add subjects here but not able to do something like

univStudent.subjects.add(new Subject{....});

How do i add items to this object array?

Answer 1

You can try

Subject[] subjects = new Subject[2];
subjects[0] = new Subject{....};
subjects[1] = new Subject{....};

alternatively you can use List

List<Subject> subjects = new List<Subject>();
subjects.Add(new Subject{....});
subjects.Add(new Subject{....});
// Then you can convert the List to Array like below:
Subject[] arraySubjects = subjects.ToArray<Subject>() 

Answer 2

You can use class System.Array for add new element:

Array.Resize(ref objArray, objArray.Length + 1);
objArray[objArray.Length - 1] = new Someobject();

Answer 3

You can't. However, you can replace the array with a new one which contains the extra element.

But it is easier and gives better performance to use an List<T> (uses interface IList) for this. List<T> does not resize the array every time you add an item - instead it doubles it when needed.

Try:

class Student
{
    IList<Subject> subjects = new List<Subject>();
}

class Subject
{
    string Name;
    string referenceBook;
}

Now you can say:

someStudent.subjects.Add(new Subject());

Answer 4

If you can, use a List<Subject> instead of Subject[]... this will let you do Student.Subject.Add(new Subject()). If that is not possible, you'll have to resize your array... look at Array.Resize() at http://msdn.microsoft.com/en-us/library/bb348051.aspx

Answer 5

I know this is old, but came across it looking for a simpler way, and this is how i do it, just create a new list of the same object and add it to the one you want to use e.g.

Subject[] subjectsList = {new Subject1{....}, new Subject2{....}, new Subject3{....}} 
univStudent.subjects = subjectsList ;

Answer 6

You can convert it ToList(), add and then convert it back ToArray().

var subjectList = univStudent.subjects.ToList();
subjectList.Add(new Subject());
univStudent.subjects = subjectList.ToArray();

Answer 7

You can create a list as follows.

List<Subject> allDestek = new List<Subject>() {
   new Subject(){ ID = 1, Name = "aaaa"},
   new Subject(){ ID = 2, Name = "bbbb"},
   new Subject(){ ID = 2, Name = "cccc"},
   new Subject(){ ID = 2, Name = "dddd"}
 };

 allSubject.ToArray()

If data is coming from somewhere (EF,SQL), you can add it in a table as follows.

Stutent[] allStudent = _dataRepository.Subjectes.ToArray();

Answer 8

`

`Here is add method in student class to add subject in student object. I also make an subject object inside student object to add in ADD function and 
I change array of subject into List of subjects.````



class Student
{
   List<Subject> subjects new List<Subject>();

public static addSubject(string name, string referenceBook){
Subject subject = new Subject();
subject.name=name;
subject.referenceBook=referenceBook;
subjects=Add(subject);
System.Console.WriteLine($"Added Subject: {name} with referenceBook: {referenceBook}");


}

class Subject
{
    string Name;
    string referenceBook;
}
class Program
{
    static void Main(string[] args)
    {

        Student student = new Student();
        Subject subject = new Subject();
       
System.Console.WriteLine(" Enter Subject name:");
                    subject.name = Console.ReadLine();
                    System.Console.WriteLine(" Enter Subject Reference Book:");
                    subject.referenceBook = Convert.ToDouble(Console.ReadLine());
                    
                    student.addSubject(subject.name, subject.referenceBook);
          }
}