c# - How to define a table that its primary key is constructed from 2 foreign keys with EF code-first -

i using models define tables using ef code-first.

i have , item model , order model.

item:

 public class item     {         public int itemid { get; set; }          [required]         public int price { get; set; }          [required]         public int amountleft { get; set; }          [required]         public string image { get; set; }          [required]         public string description { get; set; }          [required]         public string fulldescription { get; set; }          [required]         public datetime publishdate { get; set; }           public int companyid { get; set; }         public int categoryid { get; set; }          // navigation properties          public virtual company company { get; set; }          // navigation properties          public virtual category category { get; set; }       } 

order model:

public class order     {         public int orderid { get; set; }          [required]         public datetime deliverydate { get; set; }          [required]         public string currency { get; set; }          [required]         public int totalamount { get; set; }          public list<int> items { get; set; }           public datetime orderdate { get; set; }           public int userid { get; set; }         // navigation properties          public virtual user user { get; set; }      } 

i want create table called iteminorder have 2 fields: itemid , orderid. primary key these 2 foreign keys.

i tried define model:

   public class iteminorder     {          public int orderid { get; set; }         public int itemid { get; set; }          // navigation properties          public virtual order order { get; set; }         public virtual item item { get; set; }      } 

but got errors. tried put [key] notation on both fields still got errors.

how able create table want?

when need create table composite pks, need specify order of keys. there 2 variants:

you override onmodelcreating method on context, , try these fluent api configurations:

// configure primary keys iteminorder in order want modelbuilder.entity<iteminorder>()      .haskey(t => new{t.orderid,itemid);   modelbuilder.entity<iteminorder>()              .hasrequired(io=>io.order)             .withmany()             .hasforeigkey(io=>io.orderid);   modelbuilder.entity<iteminorder>()             .hasrequired(io=>io.item)            .withmany()            .hasforeigkey(io=>io.itemid); 

the second variant using data annotations should way:

[key]  [column(order=1)]  [foreignkey("order")] public int orderid { get; set; }  [key]  [column(order=2)]  [foreignkey("item")] public int itemid { get; set; } 

ef notice want create 2 relationships , job you.