Object reference not set to an instance of an object.

Question

i m looping through table to find out cell have csstdgreen. i give an error Object reference not set to an instance of an object.

 for(int i = 0; i < mytable.Rows.Count; i++)
            {
                for(int j = 0; j < mytable.Rows[i].Cells.Count; j++)
                {
                    if(mytable.Rows[i].Cells[j].Attributes["class"].Equals("csstdgreen"))
                    {

                    }
                }
            }
<table id="mytable" runat="server">
<tr class="csstablelisttd">
            <td>
                09:00AM
            </td>
            <td class="csstdgreen">
                00
            </td>
            <td class="csstdgreen" rowspan="3">
                John
            </td>
        </tr>
</table>

Why not debug it and see what is null ? is more fast and easy to debug it than ask it. — Aristos, Jul 04 '12 at 07:34
Almost all cases of `NullReferenceException` are the same. Please see "[What is a NullReferenceException in .NET?](http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-in-net)" for some hints. — John Saunders, Oct 13 '13 at 02:15

score 2 · Accepted Answer · answered Jul 04 '12 at 07:35

in this part:

<td>
    09:00AM
</td>

there is no class attribute. So you need to check if it is null first:

if (mytable.Rows[i].Cells[j].Attributes["class"] != null &&
    mytable.Rows[i].Cells[j].Attributes["class"].Equals("csstdgreen")) { 

    // other code...

}

score 1 · Answer 2 · answered Jul 04 '12 at 08:22

How about this ?

    for(int i = 0; i < mytable.Rows.Count; i++)
        {

    string cssClass ;
    for(int j = 0; j < mytable.Rows[i].Cells.Count; j++)
    {

    cssClass = mytable.Rows[i].Cells[j].Attributes["class"];

       if(cssClass != null)
        {
          if(cssClass != String.Empty)
          {}
        }

    }

}

score 0 · Answer 3 · answered Jul 04 '12 at 07:33

0

I think mytable.Rows[i].Cells[j].Attributes["class"] is null in your case.

You need check this for null

if (mytable.Rows[i].Cells[j].Attributes["class"] != null)

answered Jul 04 '12 at 07:33

Asif Mushtaq

13,010
3
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42

score 0 · Answer 4 · answered Jul 04 '12 at 07:40

0

if(Rows[i] != null)
    if(Cells[j] != null)
       if(Cells[j].Attributes["class"] != null)

answered Jul 04 '12 at 07:40

JohnnBlade

4,261
1
21
22

score 0 · Answer 5 · answered Jul 04 '12 at 07:42

0

either check for null as

if (mytable.Rows[i].Cells[j].Attributes["class"] != null)

or add a class attribute in your

<td>      09:00AM  </td>

part as

<td class="abc">      09:00AM  </td>

answered Jul 04 '12 at 07:42

akhil

1,202
3
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Object reference not set to an instance of an object.

5 Answers5