c# - Why is Entity Framework creating a discriminator column for my View Model? -

i've read quite few posts on table per type/tpt , discriminator column, but, i'm not wiser in situation.

taking example: have mvc app has model called foo. has 1 property called bar stored 1 many elsewhere.

i 1 using app , didn't want spend lot of time on it, wanted quickest way add items list in bar. because of this, made new class called fooviewmodel derived foo, , had string property called bartemp.

the basic idea can type 111, 222 , 333,444 in standard text field , have edit/create controllers clear whitespace , split list on comma.

what can't figure out view model never written ef, so, why creating discriminator column.

it looked when tried scaffold migration, event tried adding bartemp db.

i have since created new type called same, instead of deriving, have foo , bartemp properties in works expected, but, still don't happened , learn more.

it's because entityframework parses hierarchy. because current code doesn't ever save bartemp, there's nothing explicitly stopping writing:

context.bars.add(new bartemp()); 

there's nothing entityframework can detect above. so, plays safe , assumes if inherit entity, subclass also entity. that's correct assumption - , shouldn't make view models inherit entity. neither should properties. i'm unsure how you've setup current code, classes should distinct. example, should like:

class bartemp {     public string barid { get; set; }     public string foos { get; set; } }  class bar {     public string barid { get; set; }     public icollection<foo> foos { get; set; } } class foo {     public string id { get; set; }     public bar bar { get; set;  } 

your view model should know nothing entities, , entities should know nothing view models. code accepting input should work converting view model entity. example:

private void update(bartemp bartemp) {     var bar = context.bars.getbyid(bartemp.barid);     foreach (var foo in bartemp.foos.split(","))     {         var foo = context.foos.getbyid(foo);         bar.foos.add(foo);     }     context.save(); } 

don't take above example of code - it's extremely inefficient - should show example of conversions should take place, , how keep entities , view models separate.