C# uses Connection to open/close a database

To access the database, provide a database Connection class. In C#, this is done through the Connection class.

Four types of connection modes

SQLConnection ADOConnection

OractleConnection ODBCConnection

SQLConnection to the database:

SQL Server Database

Windows identity authentication

Steps:

Using system.data. SqlClient;

Declare the concatenation method in the value string

Creating a Connection object

A method is called

To save system resources and improve system performance, it is best to close the connection after using the database.

In the c # language because of the existence of GC (garbage collection) to release resources at some time in the future, it is a decisive, not sure when this process occurs, when forget to close the database can be using statements to ensure that the objects exit immediately be released, so as to close the database, and another by the try.. catch.. final.. The e statement controls the shutdown of the connected database to improve performance.

Code implementation is as follows:

using System;
using System.Data.SqlClient;   // Introduce the namespace
namespace Csharpone
{
    class Program
    {
        static void Main(string[] args)
        {
            // Windows id verify that csharp01 is a new database name
            string constr = "Server.; integrated security=SSPI; Initial Catalog=csharp01";
            SqlConnection mysqlCon = new SqlConnection(constr);  / / instantiate
            mysqlCon.Open();  // Open the database
            Console.WriteLine("Database open");    // If it is printed correctly, it is ok, otherwise an exception will be thrown

            PWD is password. Csharp02 is database name
            string constr1 = "Server.; user=name; pwd=mima; database=csharp02";
            SqlConnection mysqlCon1 = new SqlConnection(constr1);  / / instantiate
            mysqlCon1.Open();  // Open the database
            Console.WriteLine(Open database in SQL mode);
 Using (mysqlCon1) {mysqlcon1.open (); Console.WriteLine(" data opened successfully "); // Close immediately} // Pass the try.. catch.. finally.. try { mysqlCon.Open(); Console.WriteLine(" database closed "); } catch { } finally { mysqlCon.Close(); Console.WriteLine(" close database "); } * /
// Use the above two methods together to ensure that the occupied database resources are released
            try
            {
                using (mysqlCon)
                {
                    mysqlCon.Open();
 		   Console.WriteLine("Open database");
                }
            }
            catch
            {
            }
            finally
            {
                mysqlCon.Close();
 	        Console.WriteLine("Close database"); } Console.Read(); }}}Copy the code

MySQL database code:

using System;
using MySql.Data.MySqlClient;   // Import the reference and add the namespace

namespace CSharpThe connectionMysql
{
    class Program
    {
        static void Main(string[] args)
        {
            string connectStr = "server=localhost; port=3306; database=czhenya01; user=root; password=123456;";
            // No database connection has been established
            MySqlConnection conn = new MySqlConnection(connectStr);
            try
            {
                conn.Open();    // Set up the connection and open the database
                Console.WriteLine("Database opened successfully");

            }catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
            finally
            {
                conn.Close();   // Close the connection} Console.ReadKey(); }}}Copy the code