如何在 EF Core 5 请求中使用未映射的属性

Question

I need to use one condition in many places in code (frontend as well). I keep this condition like property in model. Problem is use this property for EF core request, becouse could not be translated.

Simplified example (real condition is more complex):

public class Job
{
  public DateTime? StartTime{get;set;}
  public DateTime? EndTime{get;set;}
  public bool Enabled{get;set;}

  public bool IsRunning
  {
    get{ return !EndTime.HasValue && Enabled }
  }
}

public class Repository
{
 public List<Job> GetRunningJobs
 {
  _context.Jobs.Where(j => j.IsRunning).ToList();
 }
}

What is the best approach? Thank you

Answer 1

you have to write your linq query well

public class Repository
{
 public List<Job> GetRunningJobs()
 {
     using(AppContext _context = new AppContext())
     {
       
        return _context.Jobs.Where(j => j.IsRunning == true && j.EndTime != null )
                            .ToList();
     }
 }
}

the other way is you can have another class ie JobDto (Data Transfer Object)

public class JobDto 
{ 
      public DateTime? EndTime{get;set;}
      public bool Enabled{get;set;} 
}
public class Repository
{
 public List<JobDto > GetRunningJobs()
 {
     using(AppContext _context = new AppContext())
     {
         IQueryable<JobDto> list;
                    list = from i in appContext.Jobs
                           where i.IsDeleted == null
                           && u.IsRunning == true
                           && u.EndTime != null
                           select new JobDto (){
                             EndTime= i.EndTime//set other stuff
                           };

                return list.ToList();
     }
 }
}

Answer 2

Thanks to all for your help. I used mentioned Specification pattern in this way:

 public abstract class Specification<T>
    {
      public abstract Expression<Func<T, bool>> ToExpression();    
      public bool IsSatisfiedBy(T entity)
      {
        Func<T, bool> predicate = ToExpression().Compile();
        return predicate(entity);
      }
    }

    public class RunningJobSpecification : Specification<Db.JobSetting>
    {
      public override Expression<Func<JobSetting, bool>> ToExpression()
      {
        return job => !EndTime.HasValue && Enabled;
      }
    }

public class Repository
{
 public List<Job> GetRunningJobs
 {      
  _context.Jobs.Where(j => new RunningJobSpecification().ToExpression() ).ToList();
 }
}