establishing NULL value in textbox

I have a fixed size array that is filled using items obtained from a string SPLIT.  In cases where the SPLIT results in less than five elements what are the remaining elements filled with.  In otherwords - the split of "the big dog" would result in three elements for SqlKWSearch, when the FOREACH runs what is object description of SqlKWSearch[3] and SqlKWSearch[4] ?

SqlSSelect = tbxSearchTerm.Text;
SqlKWSearch = SqlSSelect.Split(' ', ',');
int i = 0;
foreach (string a in SqlKWSearch)
{
   if (i < ...