这是现在的删除代码，如何能只删除选中的单元格而不是单元格所在整行

private void button3_Click(object sender, EventArgs e)
{



string sql = "delete from Table_2 where 1=1";
if (tb1.Text.Trim() == "")
{
MessageBox.Show("无标签可删！");
return;
}
else if (dgv1.CurrentRow.Selected)
{
sql = sql + "and ID=" + Convert.ToInt32(dgv1.CurrentRow.Cells[0].Value.ToString());
}
else {
sql = sql + "and ID=" + Convert.ToInt32(dgv1.CurrentRow.Cells[0].Value.ToString());
}

int n = 0;
SqlConnection conn = new SqlConnection(connStr);
SqlCommand cmd = new SqlCommand(sql, conn);
conn.Open();
n = cmd.ExecuteNonQuery();
if (n == 0)
{
MessageBox.Show("不存在的标签！");
return;
}
else if (n > 0)
{
MessageBox.Show("删除成功！");
}
conn.Close();
//删除完后刷新当前数据
Refresh();
}