C# DataGridView MultiSelect Cell Delete

In Windows Forms DataGridView, How Can I Delete the values of selected cells through drag?

Multiselect is applied as true in datagridview But I don't know how to delete dragged cells.

    private void DataGridView1_KeyDown(object sender, KeyEventArgs e)
    {
        switch (e.KeyCode)
        {
            case Keys.Delete:
                if (dataGridView1.Focused == true)
                {
                    dataGridView1.CurrentCell.Value = "";
                    dataGridView1.EndEdit();

                    //MultiSelect Cell Delete All Cells(Drag)
                }
                else if (dataGridView2.Focused == true)
                {
                    dataGridView2.CurrentCell.Value = "";
                    dataGridView2.EndEdit();
                }
                break;

            case Keys.Back:
                if (dataGridView1.Focused == true)
                {
                    dataGridView1.CurrentCell.Value = "";
                    dataGridView1.EndEdit();
                }
                else if (dataGridView2.Focused == true)
                {
                    dataGridView2.CurrentCell.Value = "";
                    dataGridView2.EndEdit();
                }
                break;
        }
   }