C#中连接数据库的方式

2.连接sa账户（SQL Server验证登录方式）
string constr = “Data Source =服务器;Initial Catalog=数据库名称;User Id=登录名;Password=密码”;
SQL Server验证：SQLSever2008R2为例，如图所示

实现数据库连接的C#代码如下：
1.方法1：连接数据库，返回DataTable的数据

class Sqlconnn
    {
        private static string constr = "server=.;Initial Catalog=D_total;Integrated Security=True";//本地数据库
       // private static string constr = "Data Source =192.168.1.200;Initial Catalog=D_total ;User Id=sa;Password=123456";//sa账户
        public DataTable f1()//应用实例
        {
            string A = "select * from user";
            return Conn(A);
        }
        //连接数据库，返回DataTable数据--用于查询
        public DataTable Conn(string exec)
        {
            System.Data.DataTable dt_jdl = new DataTable();
            try
            {
                using (SqlConnection con = new SqlConnection(constr))
                {
                    if (con.State == ConnectionState.Closed)
                    {
                        con.Open();
                    } if (con.State == ConnectionState.Open || con.State == ConnectionState.Connecting)
                    {
                        SqlDataAdapter sda2 = new SqlDataAdapter(exec, con);//全部通過寫存儲過程即可
                        DataSet ds2 = new DataSet();
                        sda2.Fill(ds2, "cxq");
                        dt_jdl = ds2.Tables["cxq"];
                        sda2.Dispose();
                        ds2.Dispose();
                    }
                    con.Close();
                }
                return dt_jdl;
            }
            catch (Exception EX)
            {
                return null;
            }
        }
          //通用的增删改
        public static int excuteNoQuery(string sql)
        {
            int count=0;
            try
            {
                using (SqlConnection con = new SqlConnection(constr))
                {
                    if (con.State == ConnectionState.Closed)
                    {
                        con.Open();
                    } if (con.State == ConnectionState.Open || con.State == ConnectionState.Connecting)
                    {
                        //创建命令对象
                         SqlCommand cmd = new SqlCommand(sql, con);
                         count = cmd.ExecuteNonQuery();
                         cmd.Dispose();
                    }
                    con.Close();
                }
                return count;
            }
            catch (Exception EX)
            {
                return 0;
            }         
        }   
    }

2.方法2：连接数据库方法

 class SqlCon
    {
        #region 全局变量
       //定义一个SqlConnection类型的静态公共变量My_con，用于判断数据库是否连接成功
        public static SqlConnection My_con;
        //定义数据库连接字符串
        public static string Str_sqlcon1 = "server=(local);Initial Catalog=D_total;Integrated Security=True";
        public static string Str_sqlcon2 = "Data Source=.;Database=D_total;Userid=sa;PWD=123";
        public static string Str_sqlcon3 = "Data Source =192.168.1.200;Initial Catalog=D_total ;User Id=sa;Password=123";
        #endregion
        /// 

        /// 建立数据库连接
        /// 
        /// 
        public static SqlConnection getcon()
        {
            My_con = new SqlConnection(Str_sqlcon1);//用SqlConnection对象与指定的数据库相连接  
            My_con.Open();//打开数据库连接
            return My_con;//返回SqlConnection对象信息
        }
        /// 

        /// 关闭数据库连接
        /// 
        public void con_close()
        {
            if (My_con.State == ConnectionState.Open)//判断是否打开与数据库的连接
            {
                My_con.Close();//关闭数据库的连接
                My_con.Dispose();//释放My_con变量的所有空间
            }
        }
        /// 

        /// 以只读方式读取数据库信息
        /// 
        /// 表示传递的SQL语句
        /// 
        public SqlDataReader getcom(string SQLstr)
        {
            getcon();//打开数据库连接
            SqlCommand My_com = My_con.CreateCommand();//创建SqlConnection对象，用于执行SQL语句
            My_com.CommandText = SQLstr;//获取指定的SQL语句
            SqlDataReader My_read = My_com.ExecuteReader();//执行SQL语句，生成一个SqlDataReader对象
            return My_read;
        }
        /// 

        /// 通过SqlCommand对象执行数据库中的添加、修改和删除操作
        /// 
        /// 表示传递的SQL语句
        public void getsqlcom(string SQLstr)
        {
            getcon();//打开数据库连接
            SqlCommand SQLcom = new SqlCommand(SQLstr, My_con);//创建SqlConnection对象，用于执行SQL语句
            SQLcom.ExecuteNonQuery();//执行SQL语句
            SQLcom.Dispose();//释放所有空间
            con_close();//关闭数据库连接
        }      
        /// 

        /// 通过SqlCommand对象执行数据库中的添加、修改和删除操作
        /// 
        /// 传递的SQL语句
        /// 
        /// DataSet
        public DataSet getDataSet(string SQLstr, string tableName)
        {
            getcon();//打开数据库连接
            SqlDataAdapter SQLda = new SqlDataAdapter(SQLstr, My_con);
            DataSet ds = new DataSet();//创建DataSet对象
            SQLda.Fill(ds, tableName);
            con_close();//关闭数据库连接
            return ds;//返回DataSet对象信息
        }
        /// 

        /// 通过SqlCommand对象执行数据库中的添加、修改和删除操作
        /// 
        /// 传递的SQL语句
        /// 
        /// DataTable
        public DataTable  getDataTable(string SQLstr, string tableName)
        {
            DataTable dt = new DataTable();
            getcon();//打开数据库连接
            SqlDataAdapter SQLda = new SqlDataAdapter(SQLstr, My_con);
            DataSet ds = new DataSet();
            SQLda.Fill(ds, tableName);
            dt = ds.Tables[tableName];
            con_close();//关闭数据库连接
            return dt;//返回DataSet对象信息
        }
    }

1.dll下载：https://files.cnblogs.com/yjmyzz/Oracle.ManagedDataAccess.zip
2.可以直接添加引用
3.使用代码：

 /// 

      /// oracle数据库基础类
      /// 
     
    public  class OracleHepler
    { 
          private static string connStr = "User Id=ae_re;Password=123;Data Source=(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=10.3.12.202)(PORT=1521)))(CONNECT_DATA=(SERVICE_NAME=PACKSTB)))";
        #region 执行SQL语句,返回受影响行数
        public static int ExecuteNonQuery(string sql, params OracleParameter[] parameters)
        {
            using (OracleConnection conn = new OracleConnection(connStr))
            {
                conn.Open();
                using (OracleCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);
                    return cmd.ExecuteNonQuery();
                }
            }
        }
        #endregion
        #region 执行SQL语句,返回DataTable;只用来执行查询结果比较少的情况
        public static DataTable ExecuteDataTable(string sql, params OracleParameter[] parameters)
        {
            using (OracleConnection conn = new OracleConnection(connStr))
            {
                conn.Open();
                using (OracleCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = sql;
                    cmd.Parameters.AddRange(parameters);
                    OracleDataAdapter adapter = new OracleDataAdapter(cmd);
                    DataTable datatable = new DataTable();
                    adapter.Fill(datatable);
                    return datatable;
                }
            }
        }

        #endregion
    }   

  private void button1_Click(object sender, EventArgs e)//winform程式：里面一个button和一个dataGridView
        {
            string sqlString = "select * from (select * from scqhp.cell_sort_info_by_customer) where ROWNUM<=10 ORDER BY ROWNUM asc";
            DataTable dt = OracleHepler.ExecuteDataTable(sqlString, new OracleParameter());
            dataGridView1.DataSource = dt;
        }