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  • C#教程之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。

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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<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
复制代码 代码如下:
 
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

复制代码 代码如下:

ObjectQuery<DbDataRecord> result = entities.CreateQuery<DbDataRecord>("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<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。

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