How can I define the class so that it could be initialized similarly like List<T>:
List<int> list = new List<int>(){ //this part };
e.g., this scenario:
Class aClass = new Class(){ new Student(), new Student()//... };
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Does your class inherit from IList?ken2k– ken2k2011-12-26 10:52:55 +00:00Commented Dec 26, 2011 at 10:52
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3 Answers
Typically, to allow collection-initializer syntax directly on Class, it would implement a collection-interface such as ICollection<Student>or similar (say by inheriting from Collection<Student>).
But technically speaking, it only needs to implement the non-generic IEnumerable interface and have a compatible Add method.
So this would be good enough:
using System.Collections;
public class Class : IEnumerable
{
// This method needn't implement any collection-interface method.
public void Add(Student student) { ... }
IEnumerator IEnumerable.GetEnumerator() { ... }
}
Usage:
Class aClass = new Class { new Student(), new Student() };
As you might expect, the code generated by the compiler will be similar to:
Class temp = new Class();
temp.Add(new Student());
temp.Add(new Student());
Class aClass = temp;
For more information, see section "7.6.10.3 Collection initializers" of the language specification.
2 Comments
Miro
But nor ICollection and nor IEnumarable have void Add() method, only IList has it.Does it mean that I need to implement IList (is that better practice, although your example works well)?
If you define MyClass as a collection of students:
public class MyClass : List<Student>
{
}
var aClass = new MyClass{ new Student(), new Student()//... }
Alternatively, if your class contains a public collection of Student:
public class MyClass
{
public List<Student> Students { get; set;}
}
var aClass = new MyClass{ Students = new List<Student>
{ new Student(), new Student()//... }}
Which one you select really depends on how you model a class.
Comments
I didn't see anyone suggesting generics implementation so here it is.
class Class<T> : IEnumerable
{
private List<T> list;
public Class()
{
list = new List<T>();
}
public void Add(T d)
{
list.Add(d);
}
public IEnumerator GetEnumerator()
{
return list.GetEnumerator();
}
}
and use:
Class<int> s = new Class<int>() {1,2,3,4};
