Object reference not set to an instance of an object.

Hi,

I have a picturebox in one form. When inserting data, I am filling the picturebox as well, together with other types objects, and on clikc on the picturebox I can open another window aith a whole picture of the document.
But when the data is inserted in the database, and I click on one row of the datagridview, all the objects are filled, and I want again when clicking on the picturebox to open the picture in a new window, but I get error.
"Object reference not set to an instance of an object." 
in the bold row below.

The code for the form where I open the whole picture is:

 public partial class Slik : Form
    {
        public Slik()
        {
            InitializeComponent();
            Dogovor dog = (Dogovor)Application.OpenForms["Dogovor"];
            DataGridView dgv = (DataGridView)dog.Controls["dataGridView2"];
                      
                byte[] data = (byte[])dgv.SelectedRows[0].Cells[3].Value;
                MemoryStream ms = new MemoryStream(data);
                pictureBox1.Image = Image.FromStream(ms);
           
        }

        private void Slik_Load(object sender, EventArgs e)
        {
            this.WindowState = FormWindowState.Maximized;
        }     

       
    }

and the code for the first form which calls this second form is:

private void pictureBox2_Click(object sender, EventArgs e)
        {
            if (pateka != "")
            {
                Slika slika = new Slika(izbranfajl);
                slika.Show();
            }
            else
            {
               
                Slik slika1 = new Slik();
                slika1.Show();
              
            }
        }

Can anybody help me please?Thank you in advance.

My suspicion is that no row is actually selected when that line is executed.

Try placing this line immediately above the one which is giving the error to see whether that's true or not:

MessageBox.Show(dgv.SelectedRows.Count.ToString());

Now the same error occures on that row, Object reference not set to an instance of an object.

But maybe it doesn't consider that any row is selected. When clicking on one row in the datagridview the values are retrieved and the combobox, datetimepicker, picturebox...are filled. And I want immediately to check the picture , so how can I open the picture when clicking on the picturebox in other way, or how to "repair" this one? Please tell me if you have any idea. Thanks

Ah, if you're getting the same error on the MessageBox.Show, that's telling us that 'dgv' itself is null.

Is the DataGridView placed directly on your Dogovor form or is it on some other container such as a panel, groupbox or tabpage?

Yes, The DataGridView is placed on my Dogovor form in a tabpage/tabcontrol.

OK, whilst it's still possible to do it by drilling down to the tab page which the DGV is on, a much easier way is to simply change the DGV's Modifiers property from Private to Internal. 

This can be done from its Properties Box and will make it directly visible to other forms or classes in the application.

You can then change your code to:

Dogovor dog = (Dogovor)Application.OpenForms["Dogovor"];

DataGridView dgv = dog.dataGridView2; // now accessing DGV directly

// etc.

Thank you very very much Vulpes:)