Comparison of user class objects is not supported in Linq to entities

The linq expression is:

var query = from p in _db.LogProjects

where p.Well == well

select p;

( Well is a user class )

An exception will be thrown:

Unable to create a constant value of type 'Closure type'. Only primitive types (for instance Int32, String and Guid) are supported in this context.

So, you can change the linq expression to:

var query = from p in _db.LogProjects

where p.Well.WellID == well.WellID

select p;

reference:

ADO.NET Entity Framework Comparison Frustration

Entity Framework Comparison Frustration: Explained