ADO.NET实体数据模型详细介绍

2020-01-24 03:39:25

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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<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.VeVB.COm

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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