使用实体框架查询 [英] Querying using Entity Framework
问题描述
如何查询映射到相应数据库表的实体以检索某些数据?
我有一个或者映射到数据库表的User实体用户,属性userID和用户名。
现在,我想知道通过提供userID来检索UserName的可能方法是什么。
我尝试使用下面的代码,但我不明白为什么它会显示datacontext不存在的错误。
How to query an entity that is mapped to the corresponding database table to retrieve some data?
I have a User entity which OR mapped to the database table User, which attributes userID and username.
Now, I wanted to know what are the possible ways to retrieve the the UserName by providing the userID.
I tried using the following code , but I dont understand why is it displaying an error that the datacontext does not exist.
var CurrentUserName = from c in datacontext.user
where c.UserID == someUserID
select c.Name;
推荐答案
您需要在使用之前定义datacontext:
You need to define the datacontext before using it:
datacontext = new MyEntities();
当您向项目中添加ADO.NET实体数据模型时,会创建MyEntities(您可以根据需要为其命名)。
MyEntities is created when you add an "ADO.NET Entity Data Model" to your project (you can name it whatever you want).
在下面的链接上尝试实体框架教程。非常好
http://www.entityframeworktutorial.net [ ^ ]
Try entity framework tutorial on below link. Very nice
http://www.entityframeworktutorial.net[^]
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