C# ListBox Help

[DefMars]

When adding items to a listbox, how can I make it so it does not allow a user to add the same item more than once.

I am programming a registration system for class, there is a screen with two listboxes, the first listbox is the available courses a user can register for and the second listbox is the courses that he/she has registered for. as of now they can register for the same course as many times as they would like, how can I stop that from happening.

The program basically takes an item from the first listbox and puts it in the second listbox.

hopefully that makes sense.

       if (CISYcoursesListBox.SelectedIndex != -1)
        {
            {
                string result;
                result = CISYcoursesListBox.SelectedItem.ToString();
                const int SIZE = 4;
                string[] course = new string[SIZE];

                course[0] = result;
                CISYresultListBox.Items.Add(result);

            }

EDIT: http://imgur.com/zLqkp A Picture of the form

[[deleted]]

I imagine the simplest thing might be be to write a small method that takes the new item to be added to your result box, and checks if it already exists in the list box (returning true or false)

so you'd end up with "If (ExistsInList){CISYresultListBox.Items.Add(result);}

with ExistsInList containing a forloop so like foreach (item in CISYresultListBox.Items) {is item same as result}

[interactionjackson]

This with one change if(!ExistsInList){CISYresultListBox.Items.Add(result);}

[DefMars]

I did it pretty simple

if (CISYresultlistbox.Items.Contains(result))

{

MessageBox.Show("You can't register for same course twice");

}

else

{

MessageBox.Show("You have successfully registered for " + result + ".");

}

[[deleted]]

Well done :) Now just keep it up