Removing XElements in a foreach loop

Question

So, I have a bug to remove

foreach (XElement x in items.Elements("x")) 
{
    XElement result = webservice.method(x);

    if (/*condition based on values in result*/) 
    {
     x.Remove();
    }
}

The problem is that calling x.Remove() alters the foreach such that if there are two Elements("x"), and the first is removed, the loop doesn't get to the second x element.

So how should I be looping this? Or should this be rewritten another way?

Answer 1

Create a collection before the loop logic, add the elements to be removed to the new collection, then call the items.Remove on each element in the new collection.

Answer 2

Try it without a for instead of the foreach.

Answer 3

I suspect that Linq may be able to help you out here as follows.

using System.Linq;

void foo()
{
    items.Elements("x")
         .Where(x => condition(webservice.method(x)))
         .Remove();
}

If that doesn't work (i.e. the internal enumerator is still invalidated), make a shallow copy of the selected elements and delete them as follows.

using System.Linq;

void foo()
{
    List xElements = items.Elements("x")
                          .Where(x => condition(webservice.method(x)))
                          .ToList();

    for (int i = xElements.Count; i > 0 xElements.Count; --i)
    {
        xElements[i].Remove();
    }
}