c# - 在 Entity Framework 中使用 DbContext 运行异步调用

Question

我希望能够按如下方式运行异步调用:

[Route("doit"),ResponseType(typeof(MyModel))]
public IHttpResponse PostAsyncCall(MyModel model){
    //Code removed for simplicity

    Task.Factory.StartNew(() => asyncStuff(model.id);

    return OK(model);
}

private void asyncStuff(int id) {
    MyModel model = db.MyModels.find(id);
    //Do things here. Long call to other webservices/processing of data. Time intensive normally.
    User user = db.Users.find(model.userId);
    //Do more things. Time intensive normally.
}

但是，当异步方法命中 db. 方法时，会发生错误:

An exception of type 'System.InvalidOperationException' occurred in EntityFramework.dll but was not handled in user code

Additional information: The operation cannot be completed because the DbContext has been disposed.

使用的上下文在这里:

public class MyContext : DbContext, MyContextInterface
{
        // You can add custom code to this file. Changes will not be overwritten.
        // 
        // If you want Entity Framework to drop and regenerate your database
        // automatically whenever you change your model schema, please use data migrations.
        // For more information refer to the documentation:
        // http://msdn.microsoft.com/en-us/data/jj591621.aspx

        public MyContext() : base("name=MyContext")
        {
        }

        public System.Data.Entity.DbSet<MyAPI.Models.User> Users { get; set; }

        public System.Data.Entity.DbSet<MyAPI.Models.Request> Requests { get; set; }

        public void MarkAsModified(Object item)
        {
            Entry(item).State = EntityState.Modified;
        }

    }

上下文在 Controller 中作为类变量通过以下方式创建:

private MyContextInterface db = new MyContext();

我可以看到在方法结束时正在处理数据库上下文；但是，我需要在异步方法运行期间保留此上下文以访问所需的信息。我该怎么做？

Answer 1

您启动了一项任务，但您没有等待它，因此您可以立即调用 OK。当长时间运行的任务完成时，您的数据库上下文确实已被释放。只需添加一个等待，您的问题就会得到解决。