NullReferenceException Debugging

Asked Sep 30 '16 at 21:39

Active Sep 30 '16 at 21:49

Viewed 37 times

Not a duplicate asking for debugging help, not what a Null Reference exception is.

My program is used to loop through an excel file and grab values.

In this section:

foreach (Data data in DataL)
     {
         if (data.Columns.Contains(GetColumnName(h.CellReference)[0]))
         {  
             if (h.CellValue.InnerText == " ")
             {
                 data.Items.Add(" ");
             }
             else
             {
                 data.Items.Add(GetCellV(h, ssT));
             }

The Program holds a list DataL of Data objects. Each data object has a list of items, if a cell meets the criterion it is added to the list.

However when my program reaches this point it throws me a NullReferenceException, I know this should mean my Data objects were declared and never instantiated like: Data foo = new Data();

The picture below shows that my Data List is not empty and holds the one data objected that has been created.

What is causing the exception? Is it because the object is instantiated in a different method, and is then local there?

Full code (without GUI): http://rextester.com/OIV93602

Stack Trace

edited Jun 20 '20 at 09:12

Community

asked Sep 30 '16 at 21:39

Jack Miller

2

But is the data item a null, or a real object? Next to the line that says "count = 1", click the little triangle. – Mike Dunlavey Sep 30 '16 at 21:41
its real, its been made and has properties assigned to it – Jack Miller Sep 30 '16 at 21:42
If one property is null does it make the Object null? – Jack Miller Sep 30 '16 at 21:43
1

Can you include the stack trace for the exception, please? – pquest Sep 30 '16 at 21:43
@JackMiller No, one null property does not make an entire object null. Is the type of DataL `List`? – pquest Sep 30 '16 at 21:45
What do you see if you put `DataL[0]` in the Watch window? – Mike Dunlavey Sep 30 '16 at 21:46
added Stack Trace – Jack Miller Sep 30 '16 at 21:50
Yes DataL is `public List DataL = new List();` – Jack Miller Sep 30 '16 at 21:54

NullReferenceException Debugging

0 Answers0