c# wpf listBox selectionchanged is wrongfuly (for me) fired when removing an item from obseevable collection which was already selected when removed

Question

hey guys i'v been trying to figure it out for 2 days and no luck. i have an observableCollection that stores values and presents them in list box. i want to check item int listbbox(lbBookDetails) and remove it from my collection(myBooks) using delete button.

after i press the delete buttton, i get the element of chosen index,update data for a referenced object inside my chosen Book, and the remove it.

//get chosen book
Book newBook = myBooks.ElementAt(lbBookDetails.SelectedIndex);
//take one book dowfrom authors list
getAuthorByName(newBook.author.fullName()).numOfBooks--; 
//remove the book
myBooks.Remove(myBooks.ElementAt(lbBookDetails.SelectedIndex)); //<--- problem

this line sends an event to selectionChange for some reason,and when it searches for index it gets -1 and i have "Argumentoutofrange exception"

why so?

Presumably because you have no selected item. What is the code for `selectionChange()`? — spodger, Mar 27 '18 at 11:41
Hi thanks for the comment and sorry for the delay this is the code for selectionChange() I'll write it in the comment below — Ronen, Apr 05 '18 at 09:21

score 0 · Answer 1 · answered Mar 27 '18 at 12:08

Why is exception? becouse you remove item which is selected, when u remove selected item from observableCollection then send imformation to listBox that collections was changed and item which is seleted was removed so listbox change selected index on -1 and call event selectedchange.

Tips: in future u have problem with null reference in line

myBooks.Remove(myBooks.ElementAt(lbBookDetails.SelectedIndex)); //<--- problem

u this:

var index = lbBookDetails.SelectedIndex;
myBooks.Remove(myBooks.ElementAt(index ));

Sorry for my English

thanks haqu, what are the advantages of this phrasing over the old one? — Ronen, Apr 05 '18 at 09:27

score 0 · Answer 2 · answered Apr 05 '18 at 09:24

this is the code for selectionChange()

    private void lbBookDetails_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
        var book = myBooks.ElementAt(lbBookDetails.SelectedIndex) as Book;
        if (book == null)
        {
            return;
        }

        tboAuthor.Text = book.author.fullName();      //displaying the values in case ArgumentOutOfRangeException selection from box
        tboCopies.Text = book.numOfCopys.ToString();
        tboPrice.Text = book.Price.ToString();
        tbonumByAuthor.Text = book.author.numOfBooks.ToString();

    }

c# wpf listBox selectionchanged is wrongfuly (for me) fired when removing an item from obseevable collection which was already selected when removed

2 Answers2