Remove an item from an IEnumerable<T> collection

Question

I have a popuplated IEnumerable<User> collection.

I want to remove an item from it, how can I do this?

foreach(var u in users) {   if(u.userId = 1123)   {     // remove!   } } 

I know your not suppose to remove while looping, so I don't mind either creating a new collection or removing it after.

But I don't know how to remove an item, kind of lost for some reason on this!

Alternately which I am confused on also, how can I create a new collection like:

IEnumerable<User> modifiedUsers = new List<User>();  foreach(var u in users) {    if(u.userId != 1233)    {         modifiedUsers.add ??????    } } 

How can I add to the collection?

Answer 1

Not removing but creating a new List without that element with LINQ:

// remove users = users.Where(u => u.userId != 123).ToList();  // new list var modified = users.Where(u => u.userId == 123).ToList(); 

Answer 2

You can not remove an item from an IEnumerable; it can only be enumerated, as described here: http://msdn.microsoft.com/en-us/library/system.collections.ienumerable.aspx

You have to use an ICollection if you want to add and remove items. Maybe you can try and casting your IEnumerable; this will off course only work if the underlying object implements ICollection`.

See here for more on ICollection: http://msdn.microsoft.com/en-us/library/92t2ye13.aspx

You can, of course, just create a new list from your IEnumerable, as pointed out by lante, but this might be "sub optimal", depending on your actual use case, of course.

ICollection is probably the way to go.