(2)OLEDB数据库操作

1、首先要引入 System.Data.OracleClient.dll

2、引入命名空间 using System.Data.OleDb;

OleDb类 https://msdn.microsoft.com/zh-cn/library/system.data.oledb(v=vs.110).aspx

一、连接数据库

连接字符串

 string str = "Provider=OraOLEDB.Oracle.1;User ID=xxx;Password=xxx;Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = ORCL)))";
 OleDbConnection conn = new OleDbConnection(str);

开关数据库

            conn.Open();//打开数据库连接
            conn.Close();//关闭数据库连接

打开的连接，再打开会报错。关闭的连接，再关闭不会报错。

测试连接数据库

无需配置tnsnames.ora

string str = "Provider=OraOLEDB.Oracle.1;User ID=xxx;Password=xxx;Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = ORCL)))";
 OleDbConnection conn = new OleDbConnection(str);
 conn.Open();
 if (conn.State == ConnectionState.Open)
 {
     MessageBox.Show("连接成功");
 }
 conn.Close();

ConnectionState枚举类，用来判断数据库当前状态，结果为true或false

            bool status = ConnectionState.Open;//数据库是否已打开
            bool status = ConnectionState.Closed;//数据库是否已关闭

 if (conn.State == ConnectionState.Open)
 {
     MessageBox.Show("连接成功");
 }

预定义连接字符串

1.创建一个配置文件，app.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>  
  <appSettings>
    <add key="con_MES" value="Provider=OraOLEDB.Oracle.1;User ID=MES;Password=zidonghua;Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = ORCL)))"></add>
  </appSettings>
</configuration>

2.添加 System.Configuration 程序集

3.代码增加using System.Configuration;

4.获取连接串

 string str = ConfigurationManager.AppSettings["con_MES"];

为了确保使用数据操作后不占用资源应该立即关闭连接，有两种高效使用连接的方式

1. try

 　　　　　　 string str = ConfigurationManager.AppSettings["con_MES"];
            try
            {
　　　　　　　　　　//外部以定义 OleDbConnection conn；
                conn = new OleDbConnection(str);
                conn.Open();
                if (conn.State == ConnectionState.Open)
                {
                    MessageBox.Show("连接成功");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            finally 
            {
                conn.Close();
            }

2.using

            string str = ConfigurationManager.AppSettings["con_MES"];
            using (OleDbConnection conn = new OleDbConnection(str))
            {          
                conn.Open();
                if (conn.State == ConnectionState.Open)
                {
                    MessageBox.Show("连接成功");
                }
            }

最是两者结合在一起

            string str = ConfigurationManager.AppSettings["con_MES"];
            try
            {
                using (OleDbConnection conn = new OleDbConnection(str))
                {
                    conn.Open();
                    if (conn.State == ConnectionState.Open)
                    {
                        MessageBox.Show("连接成功");
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

二、事物

ADO.NET分类里找有单独几篇博客

三、赋予命令

OleDbCommand类

表示要对数据源执行的 SQL 语句或存储过程，把SQL语句赋给Command对象

构造方法：

有四种

1、不带参　

OleDbCommand()　　　

OleDbCommand  dbsql =new OleDbCommand();

初始化时如果没带参数，可以通过属性单独添加

（1）CommandText属性：获取或设置 SQL 语句或存储的过程以对数据库执行

command.CommandText = "update pingtable set targetip='192.168.55.55' where id=1102";//添加SQL

（2）Connection属性：获取或设置 OracleCommand 的此实例使用的 OracleConnection

command.Connection = conn;//添加连接 OleDbConnection conn

（3）Transaction属性：获取或设置要在其中执行 OracleTransaction 的 OracleCommand

command.Transaction = OT; //添加事务 OleDbTransaction OT

（4）CommandType属性：获取或设置一个值，该值指示如何 CommandText 属性将被解释

　 4.1 Text 表示Command对象用于执行SQL

　　4.2 StoredProcedure表示Command对象用于执行存储过程

　　4.3 TableDirect表示Command

　　CommandType属性的默认值为Text

command.CommandType = CommandType.Text;

2、传一个参数。（一个SQL语句）

OleDbCommand(sql)

string sql="select * from tab";
OleDbCommand command=new OleDbCommand(sql);

3、传两个参数（一个sql语句和一个OleDbConnection对象）

OleDbCommand(sql,conn)

            string str = "Provider=OraOLEDB.Oracle.1;User ID=xxx;Password=xxx;Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = ORCL)))";
            OleDbConnection conn = new OleDbConnection(str);
            conn.Open();
            string sql = "select * from tab";
            OleDbCommand command = new OleDbCommand(sql, conn);
            //MessageBox.Show("成功");

4、传三个参数（一个sql语句和一个OleDbConnection对象，一个事务）

            string str = "Provider=OraOLEDB.Oracle.1;User ID=xxx;Password=xxx;Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = ORCL)))";
            OleDbConnection conn = new OleDbConnection(str);
            conn.Open();
            string sql = "select * from T_PI_ORDER";
            OleDbTransaction transaction = conn.BeginTransaction();
            OleDbCommand command = new OleDbCommand(sql, conn, transaction);
            transaction.Commit();
            MessageBox.Show("成功");

如果command构造函数时没带sql的参数，就要用CommandText属性来赋值。

            OleDbCommand command = new OleDbCommand();
            command.CommandText = "select * from tab";

如果command构造函数时没带OleDbConnection时，就给command.Connection赋值一个OleDbConnection对象。

            string str = "Provider=OraOLEDB.Oracle.1;User ID=xxx;Password=xxx;Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = ORCL)))";
            OleDbConnection conn = new OleDbConnection(str);
            conn.Open();
            OleDbCommand command = new OleDbCommand();
            command.Connection = conn;
            conn.Close();

等待命令执行所需的时间（以秒为单位）。默认值为 30 秒

            OleDbCommand command = new OleDbCommand();
            command.CommandTimeout = 1;

四、执行命令（增删改查）

1.ExecuteNonQuery()

执行 SQL 语句针并返回受影响的行数，一般用于update、insert、delete 语句的执行

            string str = "Provider=OraOLEDB.Oracle.1;User ID=xxx;Password=xxx;Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = ORCL)))";
            string sql = "update tab set score='90' where name='tom'";
            using (OleDbConnection conn = new OleDbConnection(str))
            {
                connection.Open();
                OleDbCommand command = new OleDbCommand(sql, conn);
                command.ExecuteNonQuery();
            }

2.ExecuteReader()

获得结果集,返回一个DataReader对象，一般用于select

            string str = "Provider=OraOLEDB.Oracle.1;User ID=xxx;Password=xxx;Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = ORCL)))";
            string sql = "select * from tab";
            using (OleDbConnection conn = new OleDbConnection(str))
            {
                connection.Open();
                OleDbCommand command = new OleDbCommand(sql, conn);
                OleDbDataReader reader = command.ExecuteReader();//把执行结果传给OleDbDataReader
　　　　　　　　  .......
                reader.Close();
            }

3.ExecuteScalar()

返回的数据是查询结果的第一行第一列,并且返回的结果是一个object类型,之后可以把该对象强制转换为合适的类型

            string str = "Provider=OraOLEDB.Oracle.1;User ID=xxx;Password=xxx;Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = ORCL)))";
            string sql = "select count(*) from table";
            using (OleDbConnection conn = new OleDbConnection(str))
            {
                connection.Open();
                OleDbCommand command = new OleDbCommand(sql, conn);
                object o = command.ExecuteScalar();
            }

五、调用存储过程

...

六、快速数据访问-数据读取器

OleDbDataReader类

虽然数据读取器是从数据库中选择某些数据的最简单快捷的方法。

但这也是功能最弱的方法，不能直接实例化数据阅读器，需要调用ExecuteReader()方法后从相应数据库的命令对象（如OleDbCommand）中返回的实例。

Read()方法指针移动到下一行数据之前。

while(dr.Read()) 
{
 Console.WriteLine(dr[0]);//循环输出当前行的第一列
}

            string str = "Provider=OraOLEDB.Oracle.1;User ID=xxx;Password=xxx;Data Source=(DESCRIPTION = (ADDRESS_LIST= (ADDRESS = (PROTOCOL = TCP)(HOST = 127.0.0.1)(PORT = 1521))) (CONNECT_DATA = (SERVICE_NAME = ORCL)))";
            string sql = "select * from tab";
            using (OleDbConnection conn = new OleDbConnection(str))
            {
                connection.Open();
                OleDbCommand command = new OleDbCommand(sql, conn);
                OleDbDataReader reader = command.ExecuteReader();//把执行结果传给OleDbDataReader
　　　　　　while(reader.Read())
                {
                    Console.WriteLine("'{0} from {1}',reader.GetString(0),reader.GetString(1)")
                }
                reader.Close();
            }

OleDbDataReader是一个只向前的连接读取器，即只能沿着一个方向遍历记录，而使用的数据库一直打开，直到关闭该数据读取器为止。

OleDbDataReader类不能直接实例化，需要通过调用OleDbCommand类的ExecuteReader（）方法来。

OleDbDataReader索引器取数数据

获取指定列的值,返回值是object类型

object id = dr[0];//数字索引器
object id = dr["ID"];//字符索引器

OleDbDataReader方法取数数据

reader.GetString(0)

　　　　　　while(reader.Read())
                {
                    Console.WriteLine("'{0} from {1}',reader.GetString(0),reader.GetString(1)")
                }
                reader.Close();

*用完read()方法记得Close()掉

七、填充DataSet类

从数据源读取数据并插入到DataSet中有两种方式：使用数据适配器、把XML读入DataSet

1.用数据适配器读入DataSet

这里要用到OleDbDataAdapter类，表示用于填充 DataSet 和更新数据源的一组数据命令和一个数据库连接

　　带sql语句和连接对象的初始化

　　OleDbDataAdapter(String, OleDbConnection)

            DataSet ds;
            string str = ConfigurationManager.AppSettings["con_MES"];
            try
            {
                using (OleDbConnection conn = new OleDbConnection(str))
                {
                    conn.Open();
                    if (conn.State == ConnectionState.Open)
                    {
                        string select = "select * from PINGTABLE where rownum<50";
                        OleDbDataAdapter da = new OleDbDataAdapter(select, conn);//连接对象
                        ds = new DataSet();
                        da.Fill(ds, "Costomers");
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

　　带sql语句和连接字符串的初始化

　　OleDbDataAdapter(String, String)

            DataSet ds;
            string str = ConfigurationManager.AppSettings["con_MES"];
            try
            {
                using (OleDbConnection conn = new OleDbConnection(str))
                {
                    conn.Open();
                    if (conn.State == ConnectionState.Open)
                    {
                        string select = "select * from PINGTABLE where rownum<50";
                        OleDbDataAdapter da = new OleDbDataAdapter(select, str);//连接字符串
                        ds = new DataSet();
                        da.Fill(ds, "Costomers");
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

(2)OLEDB数据库操作

OleDbParameter 类