cshtml runtime error: Only parameterless constructors and initializers are supported in LINQ to Entities - asp.net-mvc

Question

Want to use objects of a public class in cshtml, but got a runtime error: Only parameterless constructors and initializers are supported in LINQ to Entities. What is wrong with the following statement? Thanks for any help!
#foreach (var obj in ViewData["IncompleteList"] as IEnumerable<Games.TeamAction>)
The controller fills the ViewBag, like
IEnumerable<TeamAction> incomplete = dbIncAct.IncompleteActivity.Where(a => a.activityID == id)
.Select(s => new TeamAction(s.teamID, s.name, id, s.type));
ViewBag.IncompleteList = incomplete;
The class TeamAction (part of the namespace Games) is quite simple:
public class TeamAction
{
public TeamAction()
{
}
....
public int teamID {get; set;}
public string teamName { get; set; }
public int activityID { get; set; }
public int actionType { get; set; }
}

Answer 1

The answer is in the error message, once you figure out how to interpret it.
You are creating an IEnumerable via LINQ to Entities (the Entity Framework LINQ provider) like so:
IEnumerable<TeamAction> incomplete = dbIncAct.IncompleteActivity
.Where(a => a.activityID == id)
.Select(s => new TeamAction(s.teamID, s.name, id, s.type));
Note that your Select call includes a lambda expression that calls the TeamAction constructor that takes 4 parameters. As soon as you ask for the first element in the IEnumerable, LINQ tries to execute your query. At that point, it parses your lambda expression and tries to translate it into an Entity Framework query that it can run. But, as the exception message says:
Only parameterless constructors and initializers are supported
You cannot include the parameterized constructor in your LINQ query because LINQ to Entities doesn't know how to execute it. To fix the problem you have a few options.
Option One: IQueryable -> IEnumerable
The easiest way around this is to make sure the EF LINQ provider never sees the offending lambda, by forcing your IQueryable into an IEnumerable before it gets there. dbIncAct.ImcompleteActivity is probably a DbSet<>, and DbSet<>.Where returns an IQueryable that is still dependent on LINQ 2 Entities. To break that dependency, you can do:
IEnumerable<TeamAction> incomplete = dbIncAct.IncompleteActivity
.Where(a => a.activityID == id)
.AsEnumerable()
.Select(s => new TeamAction(s.teamID, s.name, id, s.type));
That will force your EF query to run up through the Where part and return an enumerable collection of IncompleteActivity entities. That thing (some internally-defined List-like object) is then used to call Select, completely apart from EF.
The downside here is that you're forcing the EF query, which probably hits a database, to happen immediately. If you don't want that, your only choice is to eliminate the parameterized constructor, using one of the other two options.
Option Two: Object Initializers
Depending on what that constructor did, you may or may not be able to easily fix it. If your constructor is just there to set properties on your newly created object, you're in luck. C# introduced the new object initializer syntax to go along with LINQ and lambdas for precisely this reason:
IEnumerable<TeamAction> incomplete = dbIncAct.IncompleteActivity
.Where(a => a.activityID == id)
.Select(s => new TeamAction
{
TeamId = s.teamID,
Name = s.name,
Id = id,
Type = s.type
});
Option Three: Refactor
If your constructor does any actual work, then you'll need to do some refactoring. Try to move as much logic into your default TeamAction() constructor as you can. You can also put some of the logic into the property setters, though you should try to minimize that as much as you can.
If your object really does require some complex initialization, the typical pattern to have an initialization method that gets called early in the life cycle, e.g:
var x = new X { ... };
x.InitializeMe();
You could do this, for example, inside your #for loop, or as a separate step immediately after you create your query.

Answer 2

Change it to object initialization instead:
IEnumerable<TeamAction> incomplete = dbIncAct.IncompleteActivity.Where(a => a.activityID == id)
.Select(s => new TeamAction { teamID = s.teamID, teamName = s.name, activityID = s.id, actionType = s.type });