int a;        //用字段a来保存索引位置
private void 查询_Click(object sender, EventArgs e)
        {
            a = comboBox1.SelectedText;     //获取选中项索引
        }
private void 删除_Click(object sender, EventArgs e)
        {
            comboBox1.Items.RemoveAt(a);         //移除
        }