Question

Resharper wanted me to change this code:

foreach (var item in cmbxColor1.Items)
{
    cmbxColor2.Items.Add(item);
    . . .

…because it said, “Possible ‘System.NullReferencesException'”

So it should be this:

foreach (var item in cmbxColor1.Items)
{
    if (null != cmbxColor2.Items)
    {
        cmbxColor2.Items.Add(item);
. . .

?

I don’t get this – how could a combobox’s Items be null, unless null == empty? And if null == empty, then that’s exactly what they [s,w]ould be when this code is called.

Answer 1

I suppose Resharper is wrong here, as Items collection of the ComboBox seems to be initialized by its constructor. That is:

ComboBox c = new ComboBox();
c.Items.Add("1");

is guaranteed to be OK.

Also only getaccessor is available for us here so that no one could replace this collection with another (or null). Though I am no quite sure, if there were a possibility to influence this collection while deriving from ComboBox (I couldn’t find smth at once), I guess even then it still remains guaranteed not null.