ExecuteReader()异常，原因竟然是数据库执行语句异常~~

//建立数据库连接
 2 
 3                     SqlConnection connet = new SqlConnection("server=(local);user id=sa;password=00;Database=YGXXXT");
 4                    
 5 
 6                     string strsql = "select * from Users where UID='" +userid.Text+"' and  UPassword= '"+userpasword .Text+" '" ;
 7 
 8                     //之前格式一直写成这样 string strsql = "select * from Users where UID=" +userid.Text+" and  UPassword= "+userpasword .Text ;
 9                 //导致 SqlDataReader reader = sqlcom.ExecuteReader();怎么都读取不了数据，但是困惑的是。reader读取不了数据的时候应该可以跳转到 login_masage.Text = "帐号密码不正确";
10                    //login_masage.Style["color"] = "red";为什么一直都是现实ExecuteReader()异常而下不去呢？？？困惑中ING~~
11                     SqlCommand sqlcom = new SqlCommand(strsql, connet);
12                     connet.Open();
13 
14 
15                     SqlDataReader reader = sqlcom.ExecuteReader();
16                    
17                     if (reader.Read())
18                     {
19                         Session["userid"] = reader["UID"];
20                         Session["userpower"] = reader["userpower"];
21                         if ((int)Session["userpower"] == 1)
22                         {
23                             Response.Redirect("Users.aspx");
24                         }
25                         else if ((int)Session["userpower"] == 2)
26                         {
27                             Response.Redirect("personnel_information.aspx");
28                         }
29                         else
30                         {
31                             Response.Redirect("commonpersonel.aspx");
32                         }
33                     }
34                     else
35                     {
36                         login_masage.Text = "帐号密码不正确";
37                         login_masage.Style["color"] = "red";
38                     }
39 
40                     connet.Close();