Object reference not set to an instance of an object.

Question

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Hello,
I am trying to change the cell color. The code run successfully and the Back color changes but after sometime i get error which is Object reference not set to an instance of an object. at line

if (theRow.Cells[colIndex].Value.ToString() == "Normal")

C#

private void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
        {
            int colIndex = e.ColumnIndex;
            int rowIndex = e.RowIndex;

if ( ! theRow.Cells[colIndex].Value.Equals(Null))
{
            if (rowIndex >= 0 && colIndex >= 0)
            {
                DataGridViewRow theRow = dataGridView1.Rows[rowIndex];


                if (theRow.Cells[colIndex].Value.ToString() == "Normal")
                {
                    theRow.DefaultCellStyle.BackColor = Color.Green;
                }


                else if (theRow.Cells[colIndex].Value.ToString() == "Critical")
                {
                    theRow.DefaultCellStyle.BackColor = Color.Red;

                }
}

Posted 10-Mar-13 22:48pm

ontheline89

Updated 11-Mar-13 21:52pm

v2

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Comments

Zoltán Zörgő 11-Mar-13 4:51am

Ant what is in the theRow.Cells[colIndex] at that point? Debug and see.

2 solutions

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Abhinav S · Accepted Answer · 2013-03-10T22:52:00

theRow.Cells[colIndex].Value appears to have become null for this particular scenario.
When you try to convert null to a string using toString, you will get this error.

Check why you are getting null in this value.
If null is unavoidable, check for null before converting to string or use Convert.ToString().

Aarti Meswania · Accepted Answer · 2013-03-10T22:55:00

Solution 3

reason is
you are getting...
theRow.Cells[colIndex].Value is NULL and you are tring to use tostring conversion method
Null.ToString()

that is error because NULL haven't a method tostring()

so,...

C#

if ( ! theRow.Cells[colIndex].Value.Equals(Null))
{
    if (theRow.Cells[colIndex].Value.ToString() == "Normal")
    {
        ...
    }
}

Happy Coding!
:)

Posted 10-Mar-13 22:55pm

Aarti Meswania

Comments

ontheline89 12-Mar-13 3:51am

Still i am getting same error.

Aarti Meswania 12-Mar-13 3:54am

check you have colindex in grid
means if you give 3 in colindex and grid have 3 columns then it will cause error
because col count begin from 0,1,2 = total 3 column now if search for colindex = 3 then nu such col in grid

ontheline89 12-Mar-13 3:57am

Thank you for your quick reply, I have 4 columns in my Grid.

Aarti Meswania 12-Mar-13 3:59am

then debug & check value of colindex it should not be greater then 3

ontheline89 12-Mar-13 4:00am

ok thank you. I will check now.