使用重叠的DbSet将DbContext拆分为多个上下文 [英] Splitting DbContext into multiple contexts with overlapping DbSets

问题描述

我有一个DbContext，它现在可以容纳+80个实体，只完成了4个主要模块，但是还有3个要去，而且它们还很大，所以最多可以容纳150个.我认为现在是划分上下文的最佳时机.每个模块都使用自己的实体，并获得自己的上下文，但是所有模块都使用一组实体，所以这里是mu问题:

I have a DbContext that houses +80 entities at the moment with only 4 of the main modules done, but there are 3 more to go, and they are quite bigger so it will get up to 150 easy. I think it is the perfect time to divide the contexts. Every module uses it's own entities and will get it's own context, but there is a group of entities that are used by all of the modules, so here is mu question:

我应该有一个MainContext包含所有重叠的实体，但是:

Should I have one MainContext that will have all of the overlapping entities but then:

• FK依赖关系会发生什么?
• 嵌套using (var db = new context)会导致多少性能问题，因为我需要从每个模块访问主上下文.

• What will happen to the FK dependencies?
• How much of a performance issue would be to have nested using (var db = new context) because I will need to access the main context from every module.

我应该在所有上下文中放置重叠的实体，但是

Should I put the overlapping entities in all of the contexts, but then

• 映射会发生什么，不是每个上下文都会尝试映射它自己的实体并得到错误吗?
• 是否应该排除重叠上下文在除其中一个上下文之外的所有上下文上的映射?

我应该呆在一个上下文中吗?

Should I stay with one context?

还有其他建议吗?

推荐答案

如果您需要使用跨多个DbContext的事务，则会遇到问题.无论所有DbContext是否都连接到同一数据库，它都将被提升为分布式事务.这使事情非常缓慢.

You will have problems if you need to use a transaction that spans more than one DbContext. It will be promoted to a distributed transaction no matter if all of the DbContexts connect to the same database. This makes things very slow.

您还将失去工作单元的好处，因为DbContext将独立跟踪其模型.

You will also lose the benefit of the unit of work because the DbContexts will track their models independently.

您仍然可以分离模型并复制共享模型.这不会导致各种DbContext中断关系或死锁，而不会超过两个人同时运行两个软件副本.

You could still separate the models and duplicate the shared ones. This will not cause the various DbContexts to break relationships or deadlock any more than two people running two copies of your software at the same time would.

但是，为了使事情易于管理，您可以保留在一个DbContext中，但是隐藏每个模块中不需要的模型.

However, to keep things manageable you can stay in one DbContext, but hide the models that are not needed in each module.

采用以下DbContext-

public class MyContext : DbContext
{
    public DbSet<Person> People { get; set; }
    public DbSet<Vehicle> Cars { get; set; }
    public DbSet<Trip> Trips { get; set; }
    public DbSet<Company> Employers { get; set; }
    public DbSet<Employee> { get; set; }
}

如果您想制作一个驾驶模块，则只能使用人"，汽车"和&"旅行.如果您需要薪资模块，则可以只使用Company，Employee和&人们.因此，您将需要以下接口:

If you wanted to make a driving module, you might only use People, Cars, & Trips. If you wanted a payroll module, you might only use Company, Employee, & People. So you would need the following interfaces:

public interface IDrivingContext
{
    DbSet<Person> People { get; }
    DbSet<Vehicle> Cars { get; }
    DbSet<Trip> Trips { get; }
}

public interface IPayrollContext
{
    DbSet<Person> People { get; }
    DbSet<Company> Employers { get; }
    DbSet<Employee> Employees { get; }
}

然后您更改上下文以实现两个接口:

Then you change your context to implement both interfaces:

public class MyContext : DbContext, IDrivingContext, IPayrollContext
{
    public DbSet<Person> People { get; set; }
    public DbSet<Vehicle> Cars { get; set; }
    public DbSet<Trip> Trips { get; set; }
    public DbSet<Company> Employers { get; set; }
    public DbSet<Employee> { get; set; }
}

使用DbContext时，仅将变量键入为IDrivingContext或IPayrollContext，具体取决于您要在其中编码的模块:

And when you use the DbContext, only type the variable as IDrivingContext or IPayrollContext, depending on which module you are coding inside of:

using (IDrivingContext db = new MyDbContext())
{
     // ...
}

using (IPayrollContext db = new MyDbContext())
{
    // ...
}

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