Three-storey architecture and four Heavenly Kings--a search

Last time we talked about how to use the three-tier architecture to remove data from a database, this time we'll talk about how to find data in a database, but in the last article it also involves finding, but that's showing all the records in the entire table, and we're going to look for one of the records we need this time.

1. UI Layer

The first is the interface, remember the first time we added the "Faye Wong" that record, today we will find it out

[CSharp]View Plaincopy

2. private void button1_click (object sender, EventArgs e)
4. {
6. //Instantiate a model object to pass information to the D layer
8. Login.Model.UserInfo user = new Login.Model.UserInfo ();
10. //Instantiate a model object to receive information from the D layer
12. Login.Model.UserInfo User = new Login.Model.UserInfo ();
16. //argument passed to the object
18. User. UserName = TxtUserName.Text.Trim ();
22. //Instantiate layer B
24. UserQuery.BLL.QueryBLL Userq = new UserQuery.BLL.QueryBLL ();
26. Try
28. {
30. //Pass the object to Layer B processing
32. user = Userq.userquery (user);
34. }
36. catch (Exception ex)
38. {
40. MessageBox.Show (ex. Message);
42. return;
44. }
50. Txtinformation.text = "user ID:" + user.id + "\ r \ n" + "user name:" + user.username + "\ r \ n" + " User password:" + USER.P  Assword + " \ r \ n" + "user Email:" + user.email;
52. }
54. }

2. The BLL layer [CSharp]View Plaincopy

2. Public class QUERYBLL
4. {
6. Public Login.Model.UserInfo userquery (Login.Model.UserInfo user)
8. {
10. //Instantiate D layer
12. UserQuery.DAL.QueryDAL userqd = new UserQuery.DAL.QueryDAL ();
14. //Instantiate users
16. Login.Model.UserInfo User = new Login.Model.UserInfo ();
18. Try
20. {
22. //Let D layer determine whether the information is correct
24. user = Userqd.querydao (user);
26. }
28. catch (Exception ex)
30. {
32. throw ex; //Throw the error message to the U-layer
34. }
38. //return user information
40. return User;
44. }
46. }

3. DAL layer

[CSharp]View Plaincopy

2. Public Login.Model.UserInfo Querydao (Login.Model.UserInfo user)
4. {
6. using (SqlConnection conn=new SqlConnection (dbutil.connstring))
8. {
10. SqlCommand cmd = conn.      CreateCommand (); //For working with databases
14. //Determine if the user name exists
16. Cmd.commandtext = @"SELECT * from USERS WHERE [email protected]";
20. //Get Query Language
22. Cmd.commandtype = CommandType.Text;
26. //Add parameters in query Language
28. Cmd. Parameters.Add (new SqlParameter ("@UserName", user.  UserName));
32. Conn. Open ();
34. //Query and return results
36. SqlDataReader reader = cmd. ExecuteReader ();
40. //Declare a return instance
42. Login.Model.UserInfo User = new Login.Model.UserInfo ();
46. Try
48. {
50. //If the user name exists, the user information is returned
52. if (reader. Read ())
54. {
56. //Get user information
58. User.ID = reader. GetInt32 (0);
60. User.username = reader. GetString (1);
62. User.password = reader. GetString (2);
66. //If the mailbox is not empty, remove
68. if (!reader. IsDBNull (3))
70. {
72. User.email = reader. GetString (3);
74. }
76. }
78. Else
80. {
82. //If not present, throw an error
84. throw New Exception ("The user does not exist!    ");
86. }
88. //Disconnect
90. Conn. Close ();
92. }
94. catch (Exception ex)
96. {
98. throw ex; //Throw the error message to D-Layer processing
100. }
102. return User; //Return user information
104. }
106. }

4. Results5. Summary

This simple query process with the letter, first we (U layer) to write the letter into the envelope (the user name into the entity), and then handed over to the postman (layer B) processing, and finally to the recipient (d) hands, after the recipient's processing, the reply (to return the information) into the envelope (return to the entity), And then sent to us by the postman, so that we can according to the reply, to make the corresponding treatment. Of course, if anything goes wrong in this process, the postman will also tell us that, like this, we can communicate conveniently through the postman, and through our cooperation we will be able to organize a complex work in an orderly way. Therefore, I believe that as long as we all work together, the world must become better.

Three-storey architecture and four Heavenly Kings--a search