Datagridview. Определить количество выбранных строк и их индексы

int selectedRowsCount = dataGridView1.SelectedRows.Count;
int firstSelectedRow = Math.Min(dataGridView1.SelectedRows[0].Index, dataGridView1.SelectedRows[selectedRowsCount - 1].Index);

        private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            ComboBox cbDgv = e.Control as ComboBox;
            cbDgv.SelectedValueChanged -= new EventHandler(CbDgv_SelectedValueChanged);
            cbDgv.SelectedValueChanged += new EventHandler(CbDgv_SelectedValueChanged);
        }
 
        //private List<int> SelectedIDs = new List<int>();
        private void CbDgv_SelectedValueChanged(object sender, EventArgs e)
        {
            dataGridView1.EditingControlShowing += new DataGridViewEditingControlShowingEventHandler(this.dataGridView1_EditingControlShowing);
            ComboBox box = sender as ComboBox;
            Debug.WriteLine(box.SelectedValue);
            object value = box.SelectedValue;
            var comboBox = (DataGridViewComboBoxEditingControl)sender;
            int rowIndex = comboBox.EditingControlRowIndex;
            int selectedRowsCount = dataGridView1.SelectedRows.Count;
            int firstSelectedRow = Math.Min(dataGridView1.SelectedRows[0].Index, dataGridView1.SelectedRows[selectedRowsCount].Index);
            var query = $"SELECT id_Object, Name_works FROM a_stroy.words_object where id_Object = {rowIndex}"; // получение данных из combobox 
            column2.DataSource = Execute(query);
            column2.DisplayMember = "Name_works";
            column2.ValueMember = "id_Object";
            //if (box.SelectedValue == null)
            //{
            //    Debug.WriteLine("Ошибка!!!!!!!!!!!!!!!!!!!!!!!!!!!");
            //}
            //else
            //{
 
            //}
        }

            // 
            // dataGridView1
            // 
            this.dataGridView1.ColumnHeadersHeightSizeMode = System.Windows.Forms.DataGridViewColumnHeadersHeightSizeMode.AutoSize;
            this.dataGridView1.Location = new System.Drawing.Point(335, 410);
            this.dataGridView1.Name = "dataGridView1";
            this.dataGridView1.RowHeadersVisible = false;
            this.dataGridView1.RowHeadersWidth = 82;
            this.dataGridView1.Size = new System.Drawing.Size(335, 181);
            this.dataGridView1.TabIndex = 15;
            this.dataGridView1.EditingControlShowing += new DataGridViewEditingControlShowingEventHandler(this.dataGridView1_EditingControlShowing);