c# - when is it mandatory to use fluent api when defining relationships -

i wonder if ever mandatory use fluent api when defining 1:m, 1:1, , m:m relationships. know fluent api provides more functionality data annotations not able do. however, if think straight relationships no additional requirement (e.g., renaming foreign keys in m:m relationships, or cascadeondelete, etc.), can rely on data annotations ? or still better use fluent api reasons?

everything can dataannotation can fluentapi, opposite not true. features available in fluentapi.

which should use?

depending on trying do.

some relationships can declared in class structure. instance, n:m relationship can declared follows:

public class foo  {     public icollection<bar> bars { get; set; } }   public class bar {     public icollection<foo> foos { get; set; } } 

ef recognize n:m: relationship , create "third table". however, if want "choose" third-table's name, have use fluentapi.

modelbuilder.entity<foo>()     .hasmany(s => s.bars)     .withmany(c => c.foos)     .map(cs =>         {             cs.mapleftkey("fooid");             cs.maprightkey("barid");             cs.totable("foobarrelationship");  }); 

dataannotation more simple fluentapi, if classes located in different assembly, have add reference of system.data.componentmodel, not nice.

fluentapi seems complicated, can dataannotation can do, , more. in addition, can use outside of class without problems. particularly, prefer fluentapi, because seems more clean , organised.

futhermore, if choose dataannotation, keep in mind might have use fluentapi well. so, if want use 1 approach, must choose fluentapi.