title: Entity Framework Collection was modified; enumeration operation may not execute
body: <p>I'm currently using EF 4.0. My objective is to delete a child collection and add new ones to same parent.</p>
  
  <pre><code> public void AddKids(int parentId, Kids newKids)
   {
      using (ModelContainer context = new ModelContainer(connectionString))
      {
          using (TransactionScope scope = new TransactionScope())
          {
              var query = from Parent _parent in context.Parents
                          where _parent.ParentId == parentId select _parent;
  
              Parent parent = query.Single();
              while (parent.Kids.Any())
              {
                  context.Kids.DeleteObject(parent.Kids.First());
              }
  
              if (newKids != null)
              {
                  foreach (Kid _kid in newKids)
                  {
                      parent.Kids.Add(new Kid
                      {
                          Age = _kid.Age,
                          Height = _kid.Height
                      });
                  }
              }
              scope.Complete();
          }
          context.SaveChanges(); //Error happens here
      }
  }
  </code></pre>
  
  <p>The error is as from the title: Collection was modified; enumeration operation may not execute.</p>
  
  <p>Any help would be appreciated.</p>