IEnumerable object a new IEnumerable object Can I do this

Question

I want to create a new instance of an object IEnumerable lt object gt   Can I do this   IEnumerable lt object gt  a   new IEnumerable lt object gt

User · Answer

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:

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>.

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();

User · Answer

No you can t since IEnumerable is an interface   You should be able to create an empty instance of most non-interface types which implement IEnumerable  e g  -  IEnumerable lt object gt  a   new object          or  IEnumerable lt object gt  a   new List lt object gt

User · Answer

It s a pretty old question  but for the sake of newcomers  this is how we can protect an IEnumerable lt T gt  from a null exception  Another word  to create an empty instance of a variable of type IEnumerable lt T gt  public IEnumerable lt T gt  MyPropertyName   get  set      Enumerable Empty lt T gt      https   docs microsoft com en-us dotnet api system linq enumerable empty view net-5 0 Cheers

User · Answer

You can do this   IEnumerable lt object gt  list   new List lt object gt    1  4  5  AsEnumerable    CallFunction list

User · Answer

No  You cannot do that  Use the following line of code instead   IEnumerable lt int gt  usersIds   new List lt int gt     1  2  3  AsEnumerable      I hope it helps

User · Answer

No IEnumerable is an interface  you can t create instance of interface  you can do something like this  IEnumerable lt object gt  a   new object 0

User · Answer

You can for example create an instance of List lt object gt   which implements IEnumerable lt object gt   Example   List lt object gt  list   new List lt object gt     list Add 1   list Add 4   list Add 5    IEnumerable lt object gt  en   list  CallFunction en

User · Answer

Another solution would be to use Empty  msdn extract   Returns an empty IEnumerable that has the specified type argument   IEnumerable lt object gt  a   Enumerable Empty lt object gt      There is a thread on SO about it  Is it better to use Enumerable Empty   as opposed to new List to initialize an IEnumerable   If you use an empty array or empty list  those are objects and they are stored in memory  The Garbage Collector has to take care of them  If you are dealing with a high throughput application  it could be a noticeable impact  Enumerable Empty does not create an object per call thus putting less load on the GC

User · Answer

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 lt T gt   If you want to stay with the interfaces in System Collections Generic  you need to use a class that implements ICollection lt T gt  like List lt T gt

User · Answer

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

[c#] IEnumerable<object> a = new IEnumerable<object>(); Can I do this?

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