. NET (C #) connecting to various databases-highlights

. NET (C #) connecting to various databases-highlights 1.c# Connection Connection access
Program code:
-------------------------------------------------------------------------------Using System.Data;
Using System.Data.OleDb;
..

String strconnection = "provider=microsoft.jet.oledb.4.0;";
strconnection = @ "Data Source=c:begaspnetnorthwind.mdb";

OleDbConnection objconnection = new OleDbConnection (strconnection);
..

Objconnection.open ();
Objconnection.close ();

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Explain:

Connecting to an Access database requires importing additional namespaces, so it is essential that you have the first two using command!

Strconnection This variable holds the connection string required to connect to the database, specifying 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, which is the data engine in access, that ASP.net is connected to the Access database.

"Data Source=c:/begaspnet/northwind.mdb" is the location that indicates the data source, and his standard form is "Data Source=mydrive:mypath/myfile.mdb".

Ps:
1. The "@" symbol after "+ =" is to prevent the "/" in the following string from being resolved to an escape character.
2. If the database file you want to connect to is in the same directory as the current file, you can also connect by using the following methods:
strconnection+= "Data source=";
Strconnection+=mappath ("Northwind.mdb");
This will save you from writing a whole lot of stuff!
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 create 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. So far, the connection to the Access database is complete.
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2.c# Connect SQL Server
Program 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 ();

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Explain:

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

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

And then there's his connection string, and we'll introduce a parameter (note: Separate the parameters by semicolons):
' User Id=sa ': The authentication user name for the connection database is SA. He also has an alias "UID", so we can also write "Uid=sa".
"Password=": The authentication password for the connection database is empty. His alias is "pwd", so we can write it as "pwd=".
Notice here that your SQL Server must have been set up with a username and password to log in, otherwise you won't be able to log in this way. If your SQL Server is set up for Windows login, you don't need to use the user ID and password here. This way to log in, and you need to use "TRUSTED_CONNECTION=SSPI" to log in.
"Initial Catalog=northwind": The data source used is the "Northwind" database. His alias is "database", this sentence can be written as "Database=northwind".
"Server =yoursqlserver": Use a server named "YourSQLServer". His alias is "Data Source", "Address", "Addr". If you are using a local database and you have defined an instance name, you can write as " server= (local)/instance name; If it is a remote server, replace "(local)" with the name or IP address of the remote server.
"Connect timeout=30": Connection timeout is 30 seconds.

Here, the constructor used to establish the connection object is: SqlConnection.
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3.c# Connect Oracle
Program code:
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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 ())//reading data, if the ODR. If Read () returns to false, it shows 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 pending research
}
Odr. Close ();
}
catch (Exception ee)
{
Response.Write (EE. message); If there is an error, output the error message
}
Finally
{
Conn. Close (); Close connection
}
}

-------------------------------------------------------------------------------

4.c# connection MySQL
Program code:
--------------------------------------------------------------------------------Using Mysqldrivercs;

Establishing a database connection
Mysqlconnection Dbconn;
Dbconn = new Mysqlconnection (new mysqlconnectionstring ("localhost", "MySQL", "Root", "", 3306). asstring);
Dbconn.open ();

Executing query statements
Mysqlcommand Dbcomm;
Dbcomm = new Mysqlcommand ("Select Host,user from User", dbconn);

Reading data
Mysqldatareader dbreader = Dbcomm.executereaderex ();

Display data
Try
{
while (Dbreader.read ())
{
Console.WriteLine ("Host = {0} and User = {1}", dbreader.getstring (0), dbreader.getstring (1));
}
}
Finally
{
Dbreader.close ();
Dbconn.close ();
}

To close a database connection
Dbconn.close ();

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5.c# Connect IBM DB2
program code:
-------------------------------------------------------------------- ------------ Oledbconnection1.open ();
//Open database connection
Oledbdataadapter1.fill (dataSet1, "address");
Fill in the DataSet
Datagrid1.databind ();
//Bind Data
Oledbconnection1.close ();
//close connection  

//Add number According to the database data
The textbox that adds the number of corresponding fields on the Web form, and a button, add the Click Response event code to the key button as follows:

this. oledbinsertcommand1.commandtext  =   "Insertsintosaddress" (NAME,
Email, age, address)   VALUES
(' +textbox1.text+ "', '" +textbox2.text+ "', '" +textbox3.text+ "', '" +textbox4.text+ ")";
OleDbInsertCommand1.Connection.Open ();
//