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

 
using (oracleentities entities = new oracleentities()) 
 { 
                user user = entities.user.first<user>(a => a.id.equals("id")); 

                entities.deleteobject(user); 

                entities.savechanges(); 
} 

using (oracleentities entities = new oracleentities())
 {
                user user = entities.user.first<user>(a => a.id.equals("id"));

                entities.deleteobject(user);

                entities.savechanges();
}

3、修改内容

 
using (oracleentities entities = new oracleentities()) 
 { 
                user user = entities.user.first<user>(a => a.user.equals("id")); 

                user.remarks = "修改了内容"; 

                entities.savechanges(); 
} 

using (oracleentities entities = new oracleentities())
 {
                user user = entities.user.first<user>(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<user> result = entities.user;//查询所有  

                foreach (user item in result) 
                { 

                } 
} 

using (oracleentities entities = new oracleentities())
 {
                objectquery<user> result = entities.user;//查询所有

                foreach (user item in result)
                {

                }
}
[/code]
（2）esql查询

objectquery<dbdatarecord> result = entities.createquery<dbdatarecord>("select value it  from  oracleentities.user as it ");

（3）按条件查

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：

 
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<dbdatarecord> query = entities.createquery<dbdatarecord>(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<dbdatarecord> query = entities.createquery<dbdatarecord>(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。