Value cannot be null. Parameter name: source
c#, entity-framework, linq, nullreferenceexception
Solution
I had this one a while back, and the answer isn't necessarily what you'd expect. This error message often crops up when your connection string is wrong.
At a guess, you'll need something like this:
<connectionStrings>
<add name="hublisherEntities" connectionString="Data Source=localhost;Initial Catalog=hublisher;Integrated Security=True;" providerName="System.Data.SqlClient" />
</connectionStrings>
<entityFramework>
<defaultConnectionFactory type="System.Data.Entity.Infrastructure.LocalDbConnectionFactory, EntityFramework">
<parameters>
<parameter value="Data Source=localhost;Initial Catalog=hublisher;Integrated Security=True" />
</parameters>
</defaultConnectionFactory>
</entityFramework>
What's happening is that it's looking for a data source in the wrong place; Entity Framework specifies it slightly differently. If you post your connection string and EF config then we can check.
Problem
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(IEnumerable`1 source, Func`2 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.