新手求助，请问以下关于c#三层架构的删除，哪里有问题？

Question

DAL层的代码：public int DeleteUserinfo(string name,string pwd){SqlConnection con = new SqlConnection("server=.;database=student;uid=sa;pwd=;");string sql = "delete from userinfo where name='" + name + "'";SqlCommand cmd = new SqlCommand(sql, con);con.Open();int r = cmd.ExecuteNonQuery();con.Close();return r;}BLL层的代码：public int DeleteUserinfo(string name){UserInfoDAL dal = new UserInfoDAL();return dal.DeleteUserinfo(name);}click中的代码：private void btnDelete_Click(object sender, EventArgs e){int id = (int)dataGridView1.SelectedRows[0].Cells[0].Value.ToString();userInfoBLL bll = new userInfoBLL();bll.DeleteUserinfo(id);}新手，哪有问题的，求解。

Answer 1

bll.DeleteUserinfo(id);常识性错误
id是int，他这里只起到索引作用
使用字符串，表示要删除的数据

Answer 2

调用BLL层的DeleteUserinfo()方法，但传进去的参数是个string型的
string name = dataGridView1.SelectedRows[0].Cell[0].Value.ToString;
int res = new userInfoBll().DeleteUserinfo(name);
记得引进BLL命名空间

Answer 3

BLL中 return dal.DeleteUserinfo(name);
DAL层DeleteUserinfo(string name,string pwd)
DAL层参数没有传对，还少传一个