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();
}
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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();
}
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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

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'";  www.weikejianghu.com

                ObjectQuery<DbDataRecord> query = entities.CreateQuery<DbDataRecord>(esql);