An unhandled exception of type 'system.stackoverflowexception' occurred in mscorlib.dll

void shapeComboBox()
       {

           string constr = @"Data Source=DESKTOP-909N2K6\SQLEXPRESS;Initial Catalog=project1;Integrated Security=True";
           using (SqlConnection conn = new SqlConnection(constr))
           {
               using (SqlDataAdapter sda = new SqlDataAdapter("SELECT shapeCode FROM shapeTable order by shapeCode asc ", conn))
               {
                   //Fill the DataTable with records from Table.
                   DataTable dt = new DataTable();
                   sda.Fill(dt);

                   //Insert the Default Item to DataTable.
                   DataRow row = dt.NewRow();
                   dt.Rows.InsertAt(row, 0);

                   //Assign DataTable as DataSource.

                   this.Shape.DisplayMember = "shapeCode"; // shape is the combobox column name
                   this.Shape.ValueMember = "shapeCode";
                   this.Shape.DataSource = dt;
               }
           }

       }

void dataGridView1_CurrentCellDirtyStateChanged(object sender, EventArgs e)
        {
            if (dataGridView1.IsCurrentCellDirty)
            {
                // This fires the cell value changed handler below
                dataGridView1.CommitEdit(DataGridViewDataErrorContexts.Commit);
            }
        }

        private void dataGridView1_CellValueChanged(object sender, DataGridViewCellEventArgs e)
        {
            int num = dataGridView1.CurrentCell.RowIndex;
            DataGridViewComboBoxCell Shape = (DataGridViewComboBoxCell)dataGridView1.Rows[num].Cells[10]; // this is the combobox datagridview cell
            DataGridViewImageCell Shape_img = (DataGridViewImageCell)dataGridView1.Rows[num].Cells[11]; // this is the datagridview image cell
            if (Shape.Value != null) // combobox selected value
            {

                // the code to display image based on the value retrieve from the combobox column
                    string constr = @"Data Source=DESKTOP-909N2K6\SQLEXPRESS;Initial Catalog=project1;Integrated Security=True";
                    using (SqlConnection conn = new SqlConnection(constr))
                    {                           
                      using (SqlCommand cmmd = new SqlCommand("SELECT shapeImage FROM shapeTable WHERE shapeCode = '" + Shape.Value + "'", conn))
                        {
                          try
                            {
                              foreach (DataGridViewRow row in dataGridView1.Rows)
                                {
                                  foreach (DataGridViewCell cell in row.Cells)
                                   {
                                     if (cell.GetType() == typeof(DataGridViewImageCell))
                                       {
                                        conn.Open(); // HERE IS WHERE THE ERROR OCCUR
                                        byte[] img = (byte[])cmmd.ExecuteScalar();
                                        MemoryStream ms = new MemoryStream(img);
                                        conn.Close();
                                        Shape_img.Value = Image.FromStream(ms);
                                        }
                                    }
                                    }
                               }
                            catch (Exception ex)
                             {
                               MessageBox.Show("Error\n" + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                              }
                           }
                        dataGridView1.Invalidate();
                    

               
            }


        }