ADO. NET Learning Series (1) and ado.net Learning Series

ADO. NET Learning Series (1) and ado.net Learning Series

I. Basics of ADO. NET

• The program interacts with the database through ADO. NET, and the SQL statement can be executed in the database through ADO. NET. ADO. NET provides a unified operation interface (ODBC) for different databases ). Another interface for database operations is JDBC.
• In ADO. NET, a link is created to SQL Server through the SqlConnection class. Sqlconnection represents a database link. resources such as links in ADO. NET all implement the IDisposable interface.
• Objects that implement the IDisposable interface must be released after use. Call the Dispose () method.
• Access the database through the connection method. The connection must be enabled and closed after use. You can enable it again after closing, which is the difference between Close and Dispose. Dispose () is to completely release resources.

Now let's test whether the database connection is successful.

1 using System; 2 using System. collections. generic; 3 using System. linq; 4 using System. text; 5 using System. threading. tasks; 6 // use ADO. NET technology, you must import these two namespaces 7 using System. data; 8 using System. data. sqlClient; 9 // 10 namespace ADO. NET111 {12 class Program13 {14 static void Main (string [] args) 15 {16 // create a database connection (connection string) 17 string sqlCon = "server = .; database = DB_MyStudentLife; uid = sa; pwd = Password_1 "; 18 SqlConnection scon = new SqlConnection (sqlCon); 19 20 // open the database connection 21 scon. open (); 22 23 // test to determine the database connection status 24 if (scon. state = ConnectionState. closed) 25 {26 27 Console. writeLine ("failed to connect to Database"); 28} 29 if (scon. state = ConnectionState. open) 30 {31 Console. writeLine ("successfully opened the database connection, connection successful"); 32} 33 Console. readKey (); 34} 35} 36}Test whether the database connection is successfully enabled. If yes, the system prompts "successful". Otherwise, the system prompts "failed ".

 

Test:

 

 

Finally, let's take a look at the internal principle of the SqlConnection object: Use the decompilation tool reflector;

1. We can see that SqlConnection inherits the DbConnection class and implements the ICloneable interface.

2. What does the ICloneable interface look like? Let's take a look at the decompilation:

3. Next, let's look at the Dbconnection class:

It can be seen that the Dbconnection class is an abstract class that inherits the Component class and implements the IDbConnection interface and the IDisposable interface. Let's take a look at the several

4. Component class:

This class also implements the IDisposable interface,

Let's take a look at the secrets inside the IDisposable interface:

It can be seen that IDisosable defines a Dispose () method that abstracts methods without return values.