Question
Which is the Best Practise in Declaring Entity FrameWork Contexts
function()
{
DBContext context = new DBContext();
//Entity code
return ;
}
or
function()
{
using(DBContext context = new DBContext())
{
//Entity code
}
}
Do we need to use using in EntityFrameWork ? If yes my 2nd question
In DataAccess Layer am executing EF and storing the result in IEnumerable inside using
MY DL
function()
{
IEnumerable something = null;
using(DBContext context = new DBContext())
{
IEnumerable something = ....
}
return something;
}
In Controller
function()
{
List some = something.ToList();
}
And in my controller am getting this as a list as i need to do some Find operation am getting
"The operation cannot be completed because the DbContext has been disposed Entity Framework"
Yes i can return a list from DL and it works fine
How do i handle this if i use using with IEnumerable?
Accepted Answer
You can avoid the lazy-loading EF behaviour by calling .ToList() on the IEnumerable before the context is disposed (i.e. within your using block)
Popular Answer
Yes, a using is the best practice because it cleans up your context. The Using statement is a shortcut for:
try {
// Execute your code inside the using statement
}
finally {
// Cleanup the context no matter what by calling .Dispose()
}
Keep in mind, your context likely returns IEnumerables and since EF supports lazy loading these objects won't be populated until you fetch them to a concrete collection (ie. yourResult.ToList()).
A common negative outcome occurs in this scenario:
public IEnumerable<Employee> GetEmployeesInAccounting()
{
using(var myContext = new MyDbContext())
{
return myContext.Employees.Where(emp => emp.Department == 'Accounting');
}
}
// Code that fails, Assuming Manager is a lazy loaded entity, this results in an exception but it compiles no problem
var acctEmps = GetEmployeesInAccounting();
var something = acctEmps.First().Department.Manager.Department;
You can avoid this by using the .Include(emp => emp.Manager) (linq extension method) and binding your result using .ToList();
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