ADO database Access class query, property extension

1 database access class queries

(1) Query A

Parameters: Query The primary key of this message;

There is a return value: The return value is an entity class;

Dr.read (); Execute again, read this line of information and put it into the users type.

        Returns the users entity class type public        users Chayi (string name)        {            users u = null;            Com.commandtext = "Select *from users where [email protected]";            Com. Parameters.clear ();            Com. Parameters.Add ("@name", name);            Conn. Open ();            SqlDataReader dr = com. ExecuteReader ();            if (Dr. HasRows)///To determine if there is a message {///                Read this line of information and put it into the users type                Dr. Read ();                U = new users ();///instantiation of                u.uname = dr[0]. ToString ();                U.umima = Convert.ToInt32 (dr[1]. ToString ());                U.unicheng = dr[2]. ToString ();                U.usex = Convert.toboolean (dr[3]. ToString ());                U.ubir = Convert.todatetime (Dr[4]. ToString ());                U.uzu = dr[5]. ToString ();                        }            Conn. Close ();            return u;        }

(2) Check all

no parameters;

There is a return value: Put the returned value into the generic collection;

Dr.read (); After a bad read, every read, put this line of data into an entity class, and then put the entity class into the generic collection.

return type generic collection public        list<users> Chasuo ()         {        list<users> list=new list<users> ();/// Instantiating a generic collection        , users u = null;          Com.commandtext = "SELECT * from users";        Conn. Open ();        SqlDataReader dr = com. ExecuteReader ();        if (Dr. HasRows)///Determine if there is a message        {while            (Dr. Read ())//loop read, each row {//                /each row of data into the entity class                U = new users ();//Instantiate entity class                U.uname = Dr[0]. ToString ();                U.umima =convert.toint32 (dr[1]. ToString ());                U.unicheng = dr[2]. ToString ();                U.usex = Convert.toboolean (dr[3]. ToString ());                U.ubir =convert.todatetime (Dr[4]. ToString ());                U.uzu = dr[5]. ToString ();                List. ADD (U); Put an entity class into the generic collection                       }                }        conn. Close ();        return list;        }

Iterating through the collection displays all the information, one line at a time of each traversal.

            List<users> List1 = Ud.chasuo ();//Call query all functions            Console.WriteLine ("name" + "\ T" + "password" + "\ T" + "nickname" + "\ T" + "gender" + " \ t "+" date of birth "+" \ T "+" national ");            if (List1. count>0)            {            foreach (Users  U1 in List1)//Traversal collection            {                    Console.WriteLine (u1.uname + "\ T" + U1.umima + "\ T "+ U1.unicheng +" \ T "+ U1.usexget +" \ T "+ u1.ubirget+" \ T "+ u1.uzuget);}                        }

　　

2 Property Extensions

(1) The member variable in the entity class is added with a read-only property, which allows the display to reach what we really want to display

Private BOOL_usex;//Private member variables Public BOOLproperties of the Usex//member variable (readable and writable) {Get{return_usex;} Set{_usex =value;} }         Public stringusexget//member variable properties (read-only) {Get{return_usex?"male":"female"; } To make the displayed content a"Male" or "female", not bool type.

}

(2) You can display the contents of a column with a foreign key relationship instead of a code name

A the foreign key joined table is written in two classes: entity class, data access class.

The data access class contains a query function: The parameter is the < outside keyword, and the return value is < What we need to display >.

B entity class Chinese and foreign keywords plus a read-only property

The query function for the table data access class that calls the foreign key join in the property, which can be changed to content when displayed.

Private string_uzu;//Private member variable Public stringuzu//property of member variable (readable writable) {Get{return_uzu;} Set{_uzu =value;} }         Public stringuzuget//member variable properties (read-only) {Get{mingzudata mz=NewMingzudata (); stringMN =Mz.cha (_uzu). mname;//calling a foreign key join table data Access class query functionreturnmn; }                }

ADO database Access class query, property extension