Ado. Net (iv)--extended attributes and profile applications

One, extended properties

Processing: A foreign key relationship will be codenamed information processing into the original text, so that users can read (rough explanation)

Leveraging extended Attributes

such as: The National column in the info table shows the national name of the national code processed into the nation table.

Need to extend a property in the info class that displays the nation name

The code shows:

Step one: Construct a code name change method in Nationda

 Public stringNationname (stringcode) {_cmd.commandtext="Select Name from Nation where [email protected]"; _cmd. Parameters.addwithvalue ("@code", code); _conn.            Open (); _DR=_cmd.            ExecuteReader (); if(_DR. HasRows) {_dr.                Read (); return_dr[0].            ToString (); }            Else            {                return "Han"; } _conn.        Close (); }

Step Two:

 public  class   Info { //  Extended Name Family Name property  public  string   Nationname { get   = new   Nationda ();  return  da. Nationname (this . Nation); // this keyword, does the object have a nation   

Ii. configuration Files (app. config)

Change the computer, the database name is not the same, in order to let other users can also run, the data connection written in the configuration file, easy to modify

Cases:

In app. config:

<?xml version="1.0"encoding="Utf-8"?><configuration> <startup> <supportedruntime version="v4.0"sku=". netframework,version=v4.5"/> </startup>//Key Configuration name<appSettings> <add key="connstring"Value="server=.; Database=mydb;user=sa;pwd=123"/> </appSettings></configuration>

In the Data connection class:

 public  class   Dbconnect { private  static  string  connstring = System.configuration.configurationsettings.appsettings[ " connstring    public  static   SqlConnection Conn { get   return  new   SqlConnection (connstring); }        }    }

A lower version can be used with this method, and a higher version can be changed as prompted:

User Modification Method:

Find the second file first:

Then, open the changes with Notepad.

Ado. Net (iv)--extended attributes and profile applications