c# - Why does EntityFramework 6 not support explicitly filtering by Discriminator? -

the following small ef6 program demonstrate issue.

public abstract class base {     public int id { get; set; }      public abstract int typeid { get; } } public class suba : base {     public override int typeid => 1; } public class subaa : suba {     public override int typeid => 2; } public class subb : base {     public override int typeid => 3; } public class subc : base {     public override int typeid => 4; }  public class devartcontext : dbcontext {     public virtual dbset<base> bases { get; set; }      public devartcontext()     {      }     protected override void onmodelcreating(dbmodelbuilder modelbuilder)     {         base.onmodelcreating(modelbuilder);          modelbuilder.entity<base>()             .map<suba>(x => x.requires(nameof(suba.typeid)).hasvalue(1))             .map<subaa>(x => x.requires(nameof(subaa.typeid)).hasvalue(2))             .map<subb>(x => x.requires(nameof(subb.typeid)).hasvalue(3))             .map<subc>(x => x.requires(nameof(subc.typeid)).hasvalue(4));     } }  public class program {     public static void main(string[] args)     {         using (devartcontext ctx = new devartcontext())         {             // prevent model-changes wrecking test             ctx.database.delete();             ctx.database.create();              var result = ctx.bases.where(x => x.typeid == 1);             // throws on materialization, why?             foreach (var entry in result)             {                 console.writeline(entry);             }         }         console.readline();     } } 

the jist of this: have tph-model explicitly configured discriminator (typeid in case). try query specific subtype using typeid because using is operator in our hypothetical example return subaas, not subas.

i modify above where(x => x suba && !(x subaa)) going break add subab, , automating building exact-filter-linq-to-entities-helper-method slow because method has decent amount of reflection. not mention generated sql of above horrendous because ef/my sql provider not optimize properly.

now trying above results in notsupportedexception being thrown when query gets materialized, states because typeid not member of entity, cannot use filtering.

i went around ways circumvent this, best thing find snippet automatically generating where(x => x suba && !(x subaa)) version solve problem, have around this.

so question is: why entityframework not support this?

this soultion working excatly wish donot change ^^ "never change running system" :)

you can use enum instead of integers, give code more type safety!

static void main(string[] args) {   using (devartcontext ctx = new devartcontext())   {     // prevent model-changes wrecking test     ctx.database.delete();     ctx.database.create();     ctx.bases.add(new suba());     ctx.bases.add(new subaa());     ctx.bases.add(new subb());      ctx.savechanges();      var result = ctx.bases.where(x => x.typeid == 1);     // throws on materialization, why?     foreach (var entry in result)     {       console.writeline(entry);     }   }    console.readline();   }   public abstract class base {   public int id { get; set; }    public virtual int typeid { get; protected set; }  } public class suba : base {   public override int typeid { get;protected set; } = 1; } public class subaa : suba {   public override int typeid { get; protected set; } = 2; } public class subb : base {   public override int typeid { get; protected set; } = 3; } public class subc : base {   public override int typeid { get; protected set; } = 4; }  public class devartcontext : dbcontext {   public dbset<base> bases { get; set; }    public devartcontext()   {   } } 

result in db:

id  typeid  discriminator 1   1       suba 2   2       subaa 3   3       subb