Value cannot be null. Parameter name: source

Question

This is probably the biggest waste of time problem I have spent hours on solving for a long time.

var db = new hublisherEntities();
establishment_brands est = new establishment_brands();

est.brand_id = 1;
est.establishment_id = 1;
est.price = collection["price"];
est.size = collection["size"];

db.establishment_brands.Add(est);
db.SaveChanges();

This gives me an error of

Value cannot be null. Parameter name: source

stacktrace of

[ArgumentNullException: Value cannot be null. Parameter name: source] System.Linq.Enumerable.Any(IEnumerable1 source, Func2 predicate) +4083335 System.Data.Entity.Internal.InternalContext.WrapUpdateException(UpdateException updateException) +87
System.Data.Entity.Internal.InternalContext.SaveChanges() +193
System.Data.Entity.Internal.LazyInternalContext.SaveChanges() +33
System.Data.Entity.DbContext.SaveChanges() +20 ... ...

I just want to add an entity to the table. The ORM is EF.

Answer 1

Somewhere inside the DbContext is a value that is IEnumerable and is queried with Any() (or Where() or Select() or any other LINQ-method), but this value is null.

Find out if you put a query together (somewhere outside your example code) where you are using a LINQ-method, or that you used an IEnumerable as a parameter which is NULL.