实体框架5-获取不相关/可导航的实体

Question

Here is my case, I just want to query the NON related / navigable properties of an entity

public IQueryable<REQUIREMENTS> GetNotAssociatedRequirements(decimal projectID, decimal useCaseID)
{
    IQueryable<REQUIREMENTS> nonRelated = context.REQUIREMENTS.Where(x => x.PROJECT_ID == projectID)
                                                              .Except(context.USE_CASES.Find(useCaseID).REQUIREMENTS);
    return nonRelated;
}

Why is this not working?

Throws error:

Unable to create a constant value of type 'SIGERE_DAL.Models.REQUIREMENTS'. Only primitive types or enumeration types are supported in this context.

Thanks

Answer 1

Try this,

IQueryable<REQUIREMENTS> nonRelated = context.REQUIREMENTS.Where(x => x.PROJECT_ID == projectID)
                                                              .Except(context.USE_CASES.Where(useCaseID).REQUIREMENTS);

Answer 2

It is because you are comparing objects. EF does not support that. It only supports comparisons involving primitive types. So you have to rewrite your query, something like:

var nonRelated = 
   context.REQUIREMENTS.Where(r => r.PROJECT_ID == projectID)
                       .Where(r => 
                       !(
                           context.USE_CASES
                                  .Where(uc => uc.UseCaseID == useCaseID)
                                  .SelectMany(uc => uc.REQUIREMENTS)
                                  .Select(r1 => r1.Id)
                        ).Any(id == r.Id)