I want to check whether checkbox in my datagridview is checked or not

for (j = 0; j < i; j++)
            {
                //MessageBox.Show(dataGridView1.Rows[j].Cells["Column8"].Value.ToString());

                if (Convert.ToBoolean(dataGridView1.Rows[j].Cells["Column8"].Value) == true)
                {
                    using (SqlConnection conn = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=C:\Users\tahathegreat\Documents\Visual Studio 2008\Projects\WindowsFormsApplication1\WindowsFormsApplication1\TT.mdf;Integrated Security=True;Connect Timeout=30;User Instance=True"))
                    {
                        conn.Open();
                        using (SqlCommand cmd = new SqlCommand("UPDATE [UInfo] SET [Checked]=@chk" + " WHERE SAPNo=@sno", conn))
                        {
                            cmd.Parameters.AddWithValue("@chk", "1");
                            cmd.Parameters.AddWithValue("@sno", dataGridView1.Rows[j].Cells["Column5"].Value);
                            int rows = cmd.ExecuteNonQuery();
                            //rows number of record got updated
                        }
                        conn.Close();
                    }
                }
            }