Exception in C# when trying to add a string to strings List

Question

I get an exception on the List.Add line when trying to run this code:

        string searchText = searchByInterestBox.Text;
        List<string> checkedItems = null;

        if (m_BusinessLogic != null)    
        {
            if (searchText != string.Empty)  
            {
                try
                {
                    interestResultBox.Items.Clear();
                    foreach (var itemChecked in InterestsCheckedListBox.CheckedItems)
                    {
                        checkedItems.Add(itemChecked.ToString());
                    }

While debugging, when reaching the last line of code (checkedItems.Add) it says "Object Reference not set to an instance of an object"

Any idea what did I do wrong with the string list?

Thanks a lot. Itzik.

Oded · Accepted Answer · 2011-06-18 13:33:22Z

5

checkedItems is null, so you are getting an exception. You need to initialize it.

Instead of:

List<string> checkedItems = null;

Do:

IList<string> checkedItems = new List<string>();

answered Jun 18, 2011 at 13:33

Oded

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Comments

fardjad · Accepted Answer · 2011-06-18 13:33:19Z

1

You shouldn't initialize the list with null:

List<string> checkedItems = new List<string>();

answered Jun 18, 2011 at 13:33

fardjad

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devprog · Accepted Answer · 2011-06-18 13:33:22Z

1

You have never created an instance of the list, try:

List<string> checkedItems = new List<string>();

answered Jun 18, 2011 at 13:33

devprog

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agent-j · Accepted Answer · 2011-06-18 13:34:16Z

1

The exception means your list has not been created yet (and is still null).

 List<string> checkedItems = new List<string>();

answered Jun 18, 2011 at 13:34

agent-j

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