实体框架改变现有DbContext的数据库 [英] Entity Framework changing database of existing DbContext

问题描述

如果我有以下代码（例如，在我的存储库的构造函数中）：

If I have the following code (for example, in the constructor of my repository):

var db = new MyDbContext();
var entity = db.Set<Customer>();

然后稍后我做：

db.Database.Connection.ConnectionString = mySQLconnectionstring;

我需要重新设置实体？

推荐答案

坏主意。您应该创建新的上下文实例：

Bad idea. You should create new context instance:

var db1 = new MyDbContext("connstr1");
var db2 = new MyDbContext("connstr2");

否则，你会得到更多的困难，而不是你假设的好处（如果有可能的话）。请注意，每个上下文实例都保留实体化实体的本地缓存并跟踪其更改。

Otherwise you'll get more difficulties, than benefits you're supposing (if this ever possible). Note, that every context instance keeps local cache of materialized entities and tracks their changes.

由于模型相同，模型构建（这在EF中是最重要的性能）只会发生一次。我无法想象，还有什么可以迫使你重新使用上下文实例。

Since the model is the same, model building (which is most significant performance hit in EF) will happen just once. I can't imagine, what else could force you to re-use context instances.

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