C # connects the code sets of access, SQL Server, Oracle, MySQL, DB2, and Sybase databases

C # Connecting code sets for class six databases

This article lists the program source code and points to note for C # connections to access, SQL Server, Oracle, MySQL, DB2, and Sybase six different databases.

1.c# Connecting to access

Program code:

Code

Using system.data;using

System.Data.OleDb;

..

String strconnection= "provider=microsoft.jet.oledb.4.0;";

Strconnection+[email protected] "Datasource=c:begaspnetnorthwind.mdb";

OleDbConnection objconnection=new OleDbConnection (strconnection);

..

Objconnection.open ();

Objconnection.close ();

Explain:

Connecting to an Access database requires importing additional namespaces, so it is essential to have the top two using commands!

Strconnection This variable contains the connection string needed to connect to the database, he specifies the data provider to use and the data source to use.

"Provider=Microsoft.Jet.OLEDB.4.0;" Refers to the data provider, which uses the Microsoft Jet engine, the data engine in access, which is connected to the database of access.

"Data Source=c:\begaspnet\northwind.mdb" is the location of the source, and his standard form is "Data Source=mydrive:mypath\myfile.mdb".

Ps:

1. The "@" symbol after "+ =" Prevents the "\" in subsequent strings from resolving to escape characters.

2. If the database file you want to connect to is in the same directory as the current file, you can also connect using the following method:

strconnection+= "Data source=";

Strconnection+=mappath ("Northwind.mdb");

3. Be aware that the parameters in the connection string are separated by semicolons.

"OleDbConnection objconnection=new OleDbConnection (strconnection);" This is the use of a defined connection string to establish a linked object, the future operation of the database we have to deal with this object.

"Objconnection.open ();" This is used to open the connection. At this point, the connection to the Access database is complete.

2.c# Connecting to SQL Server

Program code:

Code

Using System.Data;

Using System.Data.SqlClient;

..

String strconnection= "user id=sa;password=;";

strconnection+= "Initial catalog=northwind; Server=yoursqlserver; ";

strconnection+= "Connect timeout=30";

SqlConnection objconnection=new SqlConnection (strconnection);

..

Objconnection.open ();

Objconnection.close ();

Explain:

The mechanism for connecting to a SQL Server database is not much different from the mechanism for connecting to access, except for changing the parameters in the Connection object and the connection string.

First, the namespaces used to connect to SQL Server are not "System.Data.OleDb", but "System.Data.SqlClient".

Next is his connection string, we introduce a parameter (note: The parameters are separated by semicolons):

"User Id=sa": The authenticated user name for the connection database is SA. He also has an alias "UID", so this sentence we can also write "Uid=sa".

"Password=": The authentication password for the connection database is empty. His nickname is "pwd", so we can write "pwd=". Note here that your SQL Server must already have a username and password to log in, otherwise you cannot log in in such a way. If your SQL Server is set to Windows logon, then you do not need to use "User ID" and "password" to log in, but you need to use "TRUSTED_CONNECTION=SSPI" to log in.

"Initial Catalog=northwind": The data source used is the database "Northwind". His nickname is "Database", this sentence can be written as "Database=northwind".

"Server=yoursqlserver": Use a server named "YourSQLServer". His nickname is "Data Source", "Address", "Addr". If you are using a local database and you have defined the instance name, you can write as "server= (local) \ Instance name" or "(local)" to the name or IP address of the remote server if it is a remote server.

"Connect timeout=30": The connection time-out is 30 seconds.

In this case, the constructor used to establish the connection object is: SqlConnection.

3.c# Connecting Oracle

Program code:

Code

Using System.Data.OracleClient;

Using System.Data;

Add a button to the form called Button1, double-click Button1, and enter the following code

private void Button1_Click (object sender, System.EventArgs e)

{

String connectionstring= "Data Source=sky;

User=system;password=manager; ";

Write connection string

OracleConnection conn=new OracleConnection (ConnectionString);//Create a new connection

try{

Conn. Open ();

OracleCommand Cmd=conn. CreateCommand ();

cmd.commandtext= "SELECT * from MyTable";//write SQL statements here

OracleDataReader Odr=cmd. ExecuteReader ();//Create a Oracledatereader object

while (ODR. Read ())//reads data if ODR. Read () returns to False, which indicates the end of the recordset.

{

Response.Write (ODR. Getoraclestring (1). ToString ());//Output field 1, this number is the field index, how to use the field name is still to be studied

}

Odr. Close ();

}

Catch

(Exception ee)

{Response.Write (EE. Message); If there is an error, the output error message}finally{conn. Close (); Close Connection}}

4.c# connecting MySQL

Program code:

Code

Using Mysqldrivercs; Establishing a database connection

Mysqlconnection dbconn;dbconn = new Mysqlconnection (new mysqlconnectionstring ("localhost", "MySQL", "Root", "", 3306). asstring);

Dbconn.open (); Execute Query statement

Mysqlcommand Dbcomm;

Dbcomm = new Mysqlcommand ("Select Host,user from User", dbconn); Reading data

Mysqldatareader dbreader = Dbcomm.executereaderex (); Show data

try{

while (Dbreader.read ())

{

Console.WriteLine ("Host = {0} and User = {1}", dbreader.getstring (0), dbreader.getstring (1));

}

}

Finally

{

Dbreader.close ();D bconn.close ();

}//Close database connection Dbconn.close ();

5.c# Connecting IBM DB2

Program code:

Code

Oledbconnection1.open ();

Open a database connection

Oledbdataadapter1.fill (DataSet1, "Address");

Fill in the data that is obtained

Datasetdatagrid1.databind ();

Binding Data

Oledbconnection1.close ();

Close connection

Add a textbox that adds the number of corresponding fields to the Web form, and a button to add the Click Response event code for the key:

This.OleDbInsertCommand1.CommandText = "Insertsintosaddress (Name,email, age, ADDRESS)

VALUES (' "+textbox1.text+" ', ' "+textbox2.text+" ', ' "+textbox3.text+" ', ' "+textbox4.text+" ') ";

C # connects the code sets of access, SQL Server, Oracle, MySQL, DB2, and Sybase databases