developer tip
I want to create a new instance of an object IEnumerable<object>
IEnumerable<object>
Can I do this?
IEnumerable<object> a = new IEnumerable<object>();
You can for example create an instance of List<object>, which implements IEnumerable<object>. Example:
List<object>
List<object> list = new List<object>(); list.Add(1); list.Add(4); list.Add(5); IEnumerable<object> en = list; CallFunction(en);
Since you now specified you want to add to it, what you want isn't a simple IEnumerable<T> but at least an ICollection<T>. I recommend simply using a List<T> like this:
IEnumerable<T>
ICollection<T>
List<T>
List<object> myList=new List<object>(); myList.Add(1); myList.Add(2); myList.Add(3);
You can use myList everywhere an IEnumerable<object> is expected, since List<object> implements IEnumerable<object>.
(old answer before clarification)
You can't create an instance of IEnumerable<T> since it's a normal interface(It's sometimes possible to specify a default implementation, but that's usually used only with COM).
So what you really want is instantiate a class that implements the interface IEnumerable<T>. The behavior varies depending on which class you choose.
For an empty sequence use:
IEnumerable<object> e0=Enumerable.Empty<object>();
For an non empty enumerable you can use some collection that implements IEnumerable<T>. Common choices are the array T[], List<T> or if you want immutability ReadOnlyCollection<T>.
T[]
ReadOnlyCollection<T>
IEnumerable<object> e1=new object[]{1,2,3}; IEnumerable<object> e2=new List<object>(){1,2,3}; IEnumerable<object> e3=new ReadOnlyCollection(new object[]{1,2,3});
Another common way to implement IEnumerable<T> is the iterator feature introduced in C# 3:
IEnumerable<object> MyIterator() { yield return 1; yield return 2; yield return 3; } IEnumerable<object> e4=MyIterator();
Another solution would be to use Empty.
Empty
IEnumerable<object> a = Enumerable.Empty<object>();
there is a thread on SO about it : Is it better to use Enumerable.Empty() as opposed to new List to initialize an IEnumerable?
No you can't since IEnumerable is an interface.
IEnumerable
You should be able to create an empty instance of most non-interface types which implement IEnumerable, e.g.:-
IEnumerable<object> a = new object[] { };
or
IEnumerable<object> a = new List<object>();
No, You cannot do that. Use the following line of code instead:
IEnumerable<int> usersIds = new List<int>() {1, 2, 3}.AsEnumerable();
I hope it helps.
I wanted to create a new enumerable object or list and be able to add to it.
This comment changes everything. You can't add to a generic IEnumerable<T>. If you want to stay with the interfaces in System.Collections.Generic, you need to use a class that implements ICollection<T> like List<T>.
System.Collections.Generic
The main reason is we can't create object of an interface, and IEnumerable is an interface. We need to create object of the class which implements the interface. This is the main reason we can't directly create object of IEnumerable.
No IEnumerable is an interface, you can't create instance of interface
you can do something like this
IEnumerable<object> a = new object[0];
참고URL : https://stackoverflow.com/questions/4606407/ienumerableobject-a-new-ienumerableobject-can-i-do-this