1.c# Connection Connection Access
Program code:
Copy Code code as follows:
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 ();
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 Microsoft
The jet engine, which is the data engine in access, is connected to the Access database by ASP.net.
"Data
Source=c:\begaspnet\northwind.mdb "is the location that indicates the data source, and his standard form is"
Source=mydrive:mypath\myfile.mdb ".
Ps:
1. The "@" symbol at the end of "+ =" is to prevent the "\" in the subsequent 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.
2.c# Connect SQL Server
Program code:
Copy Code code as follows:
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 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):
The 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=".
Note here that your SQL
The server must have set up a username and password to log in, otherwise it cannot be logged in this way. If your SQL
Server is set up for Windows logon, you do not need to use the user
ID "and" password "in such a way that you need to use" TRUSTED_CONNECTION=SSPI "to sign 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= "or" instance name ", and 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.
3.c# Connect Oracle
Program code:
Copy Code code as follows:
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:
Copy Code code as follows:
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);
// read 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 ();
5.c# Connect IBM DB2
Program code:
Copy Code code as follows:
Oledbconnection1.open ();
Open a database connection
Oledbdataadapter1.fill (DataSet1, "address");
Fill in the dataset with the data you have obtained
Datagrid1.databind ();
Binding Data
Oledbconnection1.close ();
Close connection
Increase database data
In the Web
Add a TextBox with the number of corresponding fields on the 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+") ";
OleDbInsertCommand1.Connection.Open ();
Open connection
Oledbinsertcommand1.executenonquery ();
Execute the SQL statement
OleDbInsertCommand1.Connection.Close ();
Close connection
6.c# Connect Sybase
Program code: (OLE DB)
Copy Code code as follows:
provider=sybase.aseoledbprovider.2;initial catalog= database name; User
id= user name; data source= source; Extended properties= ""; Server NAME=IP address; Network
Protocol=winsock; Server Port address=5000;
