ADO.NET實體數據模型詳細介紹

OleDbConnection，OracleConnection 或者SqlConnection這種連接，直接執行sql語句。現在的連接方式執行sql語句有了很大的不同，下面先看看簡單的單表的增刪改查操作，然後再看多表的關聯查詢，帶參數查詢等。
一、ADO.NET Entity對單表的增刪改查
有一個表，即在工程中是一個實體user，為了測試方便，所有字段為string型。

1、增加新記錄
增加一條記錄如下：

[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、刪除內容
代碼如下：
 
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、修改內容
代碼如下：
 
using (OracleEntities entities = new OracleEntities()) 
 { 
                User user = entities.User.First<User>(a => a.User.Equals("id")); 

                user.Remarks = "修改了內容"; 

                entities.SaveChanges(); 
} 

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

                user.Remarks = "修改了內容";

                entities.SaveChanges();
}

4、查詢內容
（1）實體直接查詢
[/code] 
using (OracleEntities entities = new OracleEntities()) 
 { 
                ObjectQuery<User> result = entities.User;//查詢所有  

                foreach (User item in result) 
                { 

                } 
} 

using (OracleEntities entities = new OracleEntities())
 {
                ObjectQuery<User> result = entities.User;//查詢所有

                foreach (User item in result)
                {

                }
}
[/code]
（2）Esql查詢
代碼如下：

ObjectQuery<DbDataRecord> result = entities.CreateQuery<DbDataRecord>("select value it  from  OracleEntities.User as it ");

（3）按條件查
代碼如下：

var result = entities.User.Where(o => o.id.Equals("id"));

二、關聯查詢
比如還有個表Other與User外鍵關聯。

進行查詢如下：
代碼如下：
 
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();
                }
 }

當然這些都是最基本的用法，因為使用的Linq和ESql，在後面再Linq和ESql的用法裡再詳細說明。