ADO.NET实体数据模型详细介绍

OleDbConnection，OracleConnection 或者SqlConnection这种连接，直接执行sql语句。现在的连接方式执行sql语句有了很大的不同，下面先看看简单的单表的增删改查操作，然后再看多表的关联查询，带参数查询等。
一、ADO.NET Entity对单表的增删改查
有一个表，即在工程中是一个实体user，为了测试方便，所有字段为string型。

1、增加新记录
增加一条记录如下：

[csharp] 
using (OracleEntities entities = new OracleEntities()) 
{ 
               User uer = User.CreateUser("id", "name", "age", "1"); 

               entities.User.AddObject(user); 

               entities.SaveChanges(); 

 using (OracleEntities entities = new OracleEntities())
 {
                User uer = User.CreateUser("id", "name", "age", "1");

                entities.User.AddObject(user);

                entities.SaveChanges();
}
2、删除内容
复制代码 代码如下: 
using (OracleEntities entities = new OracleEntities()) 
 { 
                User user = entities.User.First(a => a.ID.Equals("id")); 

                entities.DeleteObject(user); 

                entities.SaveChanges(); 
} 

using (OracleEntities entities = new OracleEntities())
 {
                User user = entities.User.First(a => a.ID.Equals("id"));

                entities.DeleteObject(user);

                entities.SaveChanges();
}

3、修改内容
复制代码 代码如下: 
using (OracleEntities entities = new OracleEntities()) 
 { 
                User user = entities.User.First(a => a.User.Equals("id")); 

                user.Remarks = "修改了内容"; 

                entities.SaveChanges(); 
} 

using (OracleEntities entities = new OracleEntities())
 {
                User user = entities.User.First(a => a.User.Equals("id"));

                user.Remarks = "修改了内容";

                entities.SaveChanges();
}

4、查询内容
（1）实体直接查询
[/code] 
using (OracleEntities entities = new OracleEntities()) 
 { 
                ObjectQuery result = entities.User;//查询所有  

                foreach (User item in result) 
                { 

                } 
} 

using (OracleEntities entities = new OracleEntities())
 {
                ObjectQuery result = entities.User;//查询所有

                foreach (User item in result)
                {

                }
}
[/code]
（2）Esql查询
复制代码 代码如下:
ObjectQuery result = entities.CreateQuery("select value it  from  OracleEntities.User as it ");

（3）按条件查
复制代码 代码如下:
var result = entities.User.Where(o => o.id.Equals("id"));

二、关联查询
比如还有个表Other与User外键关联。

进行查询如下：
复制代码 代码如下: 
using (OracleEntities entities = new OracleEntities()) 
 { 
                string esql = "SELECt b.detail FROM OracleEntities.User as a,OracleEntities.Other as b where a.otherid = b.id and a.id='id'"; 

                ObjectQuery query = entities.CreateQuery(esql); 

                foreach (DbDataRecord r in query) 
                { 
                    string ss = r["detail"].ToString(); 
                } 
 } 

using (OracleEntities entities = new OracleEntities())
 {
                string esql = "SELECt b.detail FROM OracleEntities.User as a,OracleEntities.Other as b where a.otherid = b.id and a.id='id'";  www.jb51.net

                ObjectQuery query = entities.CreateQuery(esql);

                foreach (DbDataRecord r in query)
                {
                    string ss = r["detail"].ToString();
                }
 }

当然这些都是最基本的用法，因为使用的Linq和ESql，在后面再Linq和ESql的用法里再详细说明。