MVC C# Select Where - asp.net-mvc

Question

I am trying to add filter by ID for the following:
public ActionResult Index()
{
var model = from o in new MainDBContext().OffLinePayments
select new EditOffLinePayment
{
ID = o.ID,
Amount = o.Amount
};
return View(model);
}
What I would like to do is the following:
public ActionResult Index(long? id)
{
if (id != null)
{
var model = from o in new MainDBContext().OffLinePayments
**Where Assigned_ID == id**
select new EditOffLinePayment
{
ID = o.ID,
Amount = o.Amount
};
return View(model);
}
else
{
var model = from o in new MainDBContext().OffLinePayments
select new EditOffLinePayment
{
ID = o.ID,
Amount = o.Amount
};
return View(model);
}
}

Answer 1

try
var model = from o in new MainDBContext().OffLinePayments
where o.Assigned_ID == id
select new EditOffLinePayment
{
ID = o.ID,
Amount = o.Amount
};

Answer 2

If I understand correctly, your problem is that the compiler doesn't let you write where o.Assigned_ID == id in the query.
That's because id is a Nullable<long>, which is not implicitly convertible to a long (which OffLinePayment.Assigned_ID presumably is).
You need to write where o.Assigned_ID == id.Value instead. Take a look at what the Value property does so that you don't get any surprises.

Answer 3

A cleaner, shorter and much more readable syntax would look like this:
public ActionResult Index(long? id){
using (var ctx = new MainDBContext())
{
var entities = ctx.OfflinePayments.Where(e => !e.HasValue || e.Assigned_ID == id.Value);
var model = entities.Select(e => new EditOfflinePayment { ID = e.ID, Amount = e.Amount }).ToList();
return View(model);
}
}