Object reference not set to an instance of an object

Question

Hai,

In my code while executing a function i got regularly the exception error as "Object reference not set to an instance of an object"

The function exceuting is as follows

private void PageHeaderSetting(Graphics g)
        {
            try
            {
                DataTable dtPageHeader=new DataTable() ;
                dtPageHeader = ds.Tables["Page Header"];
                if (dtPageHeader.Rows.Count != 0)
                {
                    foreach (DataRow dr in dtPageHeader.Rows)
                    {
                        if (dr.ItemArray[0].ToString() != "")
                            PageHeaderText = dr.ItemArray[0].ToString();
                        else
                            PageHeaderText = "";
                        if (dr.ItemArray[1].ToString() != "")
                            PageHeaderFont = (Font)dr.ItemArray[1];
                        else
                            PageHeaderFont = new Font("Tahoma", 18, FontStyle.Bold, GraphicsUnit.Point);
                        if (dr.ItemArray[2].ToString() != "")
                            PageHeaderFormat = AlignmentSetting(dr.ItemArray[2].ToString());
                        else
                            PageHeaderFormat = AlignmentSetting(Convert.ToString(Alignment.Left));
                        if (dr.ItemArray[3].ToString() != "")
                            PageHeaderColor = (System.Drawing.Color)dr.ItemArray[3];
                        else
                            PageHeaderColor = Color.Black;

                        PageFooterText = Word_Wrap(PageHeaderText, PageHeaderFont, g, 0);
                        PageHeader(g);
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
        }

How can i solve this.Can anybody help me?

From the second line i got the exception error means after declaring the datatable and putting the ds.Tables in it from there erroe occurs

It would help if you told us where (on what line) the error occurred. Also you have variables (like "ds") that appear "out of the blue". — Hans Keﬆing
– Hans Keﬆing, Commented Sep 9, 2009 at 9:51
Minor remark: you don't need the "new DataTable()" as you overwrite that in the next line. Just a DataTable dtPageHeader=ds.Tables["Page Header"]; is enough. — Hans Keﬆing
– Hans Keﬆing, Commented Sep 9, 2009 at 15:45

thecoop · Accepted Answer · 2009-09-09 09:59:43Z

6

This exception means you're trying to call a method on a null object. The exception should have given you a stack trace with the line number it was thrown at; this'll help you pin it down a bit. You could also try debugging it in visual studio and see where the exception is thrown & see what is null.

edited Sep 9, 2009 at 9:59

answered Sep 9, 2009 at 9:49

thecoop

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Comments

Rune Grimstad · Accepted Answer · 2009-09-09 10:01:54Z

4

Instead of using ToString() to check if you have a value in the ItemArray you should check the actual value. Check for ItemArray[0] == null and ItemArray[0] == DBNull.Value.

Edit: From your comment it seems that there may not be any data table named "Page Header" in your data set.

Try to add a null check to your DataTable object after the line dtPageHeader = ds.Tables["Page Header"];

Something like this:

if (dtPageHeader == null) 
{ 
   // There is no table named Page Header
}

edited Sep 9, 2009 at 10:01

answered Sep 9, 2009 at 9:50

Rune Grimstad

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Comments

Brian Rasmussen · Accepted Answer · 2009-09-09 09:50:50Z

1

Look at the line number in the exception.

Your code has numerous chained calls, which is a common source of this exception. If either of these chained properties returns null, the "next" call in the chain will fail with a NullReferenceException.

answered Sep 9, 2009 at 9:50

Brian Rasmussen

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Comments

Sergio · Accepted Answer · 2009-09-09 09:50:33Z

0

One of this could be true:

ds is null
A Value on a columun in dtPageHeader is null

answered Sep 9, 2009 at 9:50

Sergio

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