各类数据库的连接

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();

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();

strConnection+="Data Source=";
  strConnection+=MapPath("Northwind.mdb");

using System.Data.OracleClient;
  using System.Data;

//在窗体上添加一个按钮，叫Button1，双击Button1，输入以下代码

private void Button1_Click(object sender,  System.EventArgs e)
  {
  string ConnectionString="Data  Source=sky;user=system;password=manager;";//写连接串
  OracleConnection conn=new OracleConnection(ConnectionString);//创建一个新连接
  try
  {conn.Open();
  OracleCommand cmd=conn.CreateCommand();
  cmd.CommandText="select * from MyTable";//在这儿写sql语句
  OracleDataReader odr=cmd.ExecuteReader();//创建一个OracleDateReader对象
  while(odr.Read())//读取数据，如果odr.Read()返回为false的话，就说明到记录集的尾部了           

{
  Response.Write(odr.GetOracleString(1).ToString());//输出字段1，这个数是字段索引，具体怎么使

用字段名还有待研究
  }
  odr.Close();
  }
  catch(Exception ee)
  {
  Response.Write(ee.Message); //如果有错误，输出错误信息
  }
  finally
  {
  conn.Close(); //关闭连接
  }
  }

using MySQLDriverCS;

// 建立数据库连接
  MySQLConnection DBConn;
  DBConn = new MySQLConnection(new MySQLConnectionString

("localhost","mysql","root","",3306).AsString);
  DBConn.Open();

// 执行查询语句
  MySQLCommand DBComm;
  DBComm = new MySQLCommand("select Host,User from user",DBConn);

// 读取数据
  MySQLDataReader DBReader = DBComm.ExecuteReaderEx();

// 显示数据
  try
  {
  while (DBReader.Read())
  {
  Console.WriteLine("Host = {0} and User = {1}",

DBReader.GetString(0),DBReader.GetString(1));
  }
  }
  finally
  {
  DBReader.Close();
  DBConn.Close();
  }

//关闭数据库连接
  DBConn.Close();

OleDbConnection1.Open();
  //打开数据库连接
  OleDbDataAdapter1.Fill(dataSet1,"Address");
  //将得来的数据填入dataSet
  DataGrid1.DataBind();
  //绑定数据
  OleDbConnection1.Close();
  //关闭连接

//增加数据库数据
  在Web Form上新增对应字段数量个数的TextBox，及一个button，为该按键增加Click响应事件代码如下：

this.OleDbInsertCommand1.CommandText =  "INSERTsintosADDRESS(NAME,
  EMAIL, AGE, ADDRESS) VALUES
  ('"+TextBox1.Text+"','"+TextBox2.Text+"','"+TextBox3.Text+"','"+TextBox4.Text+"')";
  OleDbInsertCommand1.Connection.Open();
  //打开连接
  OleDbInsertCommand1.ExecuteNonQuery();
  //执行该SQL语句
  OleDbInsertCommand1.Connection.Close();
  //关闭连接

Provider=Sybase.ASEOLEDBProvider.2;
  Initial Catalog=数据库名;
  User ID=用户名;Data Source=数据源;
  Extended Properties="";
  Server Name=ip地址;
  Network Protocol=Winsock;
  Server Port Address=5000;