Applying string.IsNullorEmpty over an object

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C#

Hi All,

I am having a problem when I try to apply the method string.IsNullorEmpty() over an object, in my case, a dataGridView Cell.

My method verifies 2 cells of each line of a dataGridView and check if both Cells are filled if one of them is.

The problem is that when I use the code below...

for (int i = 0; i < dataGridView1.Rows.Count; i++)
            {
                if(!string.IsNullOrEmpty(dataGridView1.Rows[i].Cells["Column1"].Value.ToString()) && string.IsNullOrEmpty(dataGridView1.Rows[i].Cells["Column2"].Value.ToString()))
                {
                    MessageBox.Show("Please, enter a valid value for each description.");
                    return;
                }
                if(!string.IsNullOrEmpty(dataGridView1.Rows[i].Cells["Column2"].Value.ToString()) && string.IsNullOrEmpty(dataGridView1.Rows[i].Cells["Column1"].Value.ToString()))
                {
                    MessageBox.Show("Please, enter a valid description for each value.");
                    return;
                }
            }

I have the error Object reference not set to an instance of an object..

I know why it happens, but, I can't verify this cell using only

!string.IsNullOrEmpty(dataGridView1.Rows[i].Cells["Column2"].Value)<br />

... I have to use .ToString() after .Value, but, when I execute the code, it can't convert a null value to a string for it to use the method string.IsNullorEmpty().

How can I make it happens without have to error Object reference not set to an instance of an object.?

Thanks is advance! :)