How to connect to database in C#? The difference between OleDbConnection and SqlConnection

C#How to connect to the database? This article brings you the operation of C#OleDbConnection to connect to the database, so that you can understand the difference between OleDbConnection and SqlConnection. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

OleDbConnection is suitable for connecting to any type of database (such as Oracle, SQL Server, ACCESS, etc.), and its namespace is: using System.Data.OleDb;. SqlConnection is specially used to connect to SQL Server (MS SQL) database, and its namespace is: using System.Data.SqlClient.

In the operation of the database, if OleDbConnection is used, then the operation of the database, such as the connection pool, will use OleDbDataAdapter and the operation command will use OleDbCommand. Similarly, when using SqlConnection, it will be used. SqlDataAdaper and SqlcCommand. Under certain circumstances, if you need to operate on data specific to a certain field in the data table (for example, if you want to get specific data in a certain row or column), OleDbConnection can use OleDbDataReader, and SqlConnection can use the SqlDataReader reader to process data. Read.
Secondly, for the above two situations, you can also use the joint use of connection pool, dataset and datetable to obtain the specific data of a certain row and column that you want. For the use of the above specific methods and attributes, please refer to MSDN. explain!

For different .net data providers, ADO.NET uses different Connection objects to connect to the database. These Connections shield us from specific implementation details and provide a unified implementation method.

There are four types of Connection classes: SqlConnection, OleDbConnection, OdbcConnection and OracleConnection.

The object connection of the Sqlconnection class is a SQL Server database; the object connection of the OracleConnection class is connected to the Oracle database; the OleDbConneetion connection supports OLE DB databases, such as Access; and the object connection of the OdbcConnection class supports ODBC databases. All communication with the database is done through the Connection object.

This time I will introduce the use of OleDbonnection to link various data sources.

ADO.Net's data access objects include Connection, Command, DataReader and DataAdaper, etc. Since each .NET Data Provider has its own data access object, they are used in similar ways. Here we mainly introduce the use of various data access objects of OLEDB.NET Data Provider.

Note: The namespace of the OLEDB.NET data provider is System.Data.OleDb. When using it, you should add this statement in the reference section.

OleDbConnection object

In data access, a physical connection to the database must first be established. OLEDB.NET Data Provider uses objects of the OleDbConnection class to identify the physical connection to a database.

1. OledbConnection class

The common attributes of the OledbConnection class are shown in the following table. The value of the State attribute and its description are shown in Table 14.7 shown.

Commonly used properties of the OleDbConnection class and their descriptions

Property description

ConnectionString Gets or sets the string used to open the database

ConnectionTimeOut Gets the time to wait before terminating the attempt and generating an error when trying to establish a connection

Database Gets the current database or the name of the database to be used after the connection is opened

DataSource Gets the server name of the data source or filename

Provider Gets the name of the OLEDB provider specified in the "Provider = " clause of the connection string

State Gets the current state of the connection

State enumeration member value:

Connecting The connection object is connecting to the data source

Executing The connection object is executing the command

Fetching The connection object is retrieving data

Open The connection object is in the open state

The common methods of the OleDbConnection class are as shown in the following table:

Open Use the property settings specified by ConnectionString to open the database connection

Close Closes the connection to the database, this is the preferred method of closing any open connection

CreateCommand Creates and returns an OleDbCommand object associated with the OleDbConnection

ChangeDatabase Changes for the open OleDbConnection Current database

2. Establish connection string ConnectionString

The core of establishing connection is to establish connection string ConnectionString. There are two main resume connections: method.

1), directly establish the connection string

The way to directly establish the connection string is to first create an OleDbConnection object and set its ConnectionString property as follows:

Provider = Microsoft.Jet.OLEDB.4.0;Data Sourse = Access database;UserId = username;Password = password;

Among them, Provider and DataSource are required. If the Access database does not have a password, UserId and Password can be omitted. Since the Access database is a file-based database, the property value of the Data Source should be converted to the absolute path of the server in the actual project.

Finally use the Open method to open the connection.

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