急切加载在EF 6中不起作用

Question

I am having a method that returns me a list of employees.

public Employee GetAdminTypeAndPermission(int userID)
{
    using (var unitOfWork = new EFUnitOfWork())
    {
        var employeeRepo =
            new EmployeeRepository(new EFRepository<Employee>(), unitOfWork);

        DbSet<Employee> employeeObjSet =
            ((EmployeeEntities)employeeRepo.Repository.UnitOfWork.Context).Employees;

        return employeeObjSet.Where(emp => emp.FK_UserID == userID).
            Include("AdminType.Permissions").FirstOrDefault();
    }
}

In another method I am trying to use like,

var employee= GetAdminTypeAndPermission(loginInfo.UserID);
var permission = employee.AdminType.Permissions.FirstOrDefault();

I am getting an error at the following line:

var permission = employee.AdminType.Permissions.FirstOrDefault();

The ObjectContext instance has been disposed and can no longer be used for operations that require a connection. I understand the Context object disposes after the end of using block but I am using Eager loading to access the Navigation properties and I should get the result set.

Please help me in understanding what mistake I am doing here and how should I correct.

Any help is highly appreciated. Thanks in advance.

Answer 1

You have your DbContext in a using statement:

using (var unitOfWork = new EFUnitOfWork())

Once you get out of this using statement, your connection to the database is effectively closed. Either:

• Query the information you need while inside your function (and inside your using statement) or

• Pass in the DbContext to the method so you can continue to use it:

   using (var unitOfWork = new EFUnitOfWork()) { var employee= GetAdminTypeAndPermission(loginInfo.UserID, unitOfWork); //DbContext passed in var permission = employee.AdminType.Permissions.FirstOrDefault(); } 

Answer 2

Well, maybe you got the related table name wrong? What I mean, stringly typed stuff is hard to control in your code, ie is it maybe (Permission without the last 's'?):

return employeeObjSet.Where(emp => emp.FK_UserID == userID).
            Include("AdminType.Permission").FirstOrDefault();

For this kind of error I would advise you to use the lambda extension property name resolver, ie the overload/extension of the Include method which will be included if you enter the following using directive:

using System.Data.Entity;

This is the extension I tend to use:

public static IQueryable<T> Include<T, TProperty>(this IQueryable<T> source, Expression<Func<T, TProperty>> path);

It's used like this:

return employeeObjSet.Where(emp => emp.FK_UserID == userID).
        Include(x => x.Permissions).FirstOrDefault();

Here its x.Permission s because of the ICollection pluralization of the ef generator or your cf coding standard you use.

Hope it helps.