Entity framework want to say love you not easy, so many error, so many limitations, how to solve?

First look at the Entity model object diagram that was designed in the form of model one:

Note: There are navigation properties in Entityone: Entitytwo

In the following code in several cases of new operations, will be error, the new will not succeed:

 static void Main (string[] args) {Model1container context = new Model1container (); First case: Entityone has the navigation property Entitytwo, the new must also specify the new Entitytwo, otherwise error: "Model1container.entityones" in the entity participation " Entityoneentitytwo "relationship. Found 0 related "Entitytwo".            There should be 1 "entitytwo". var Objsetone = context.            Entityones;            Objsetone.mergeoption = mergeoption.notracking;            Objsetone.addobject (New Entityone () {ID = 2, P1 = "Pp1", P2 = "Pp2", P3 = "pp3"}); Context.                       SaveChanges (); The second case: sometimes our entitytwo may need to be created first, but this is done with the same error: the entity in "Model1container.entitytwos" participates in the "entityoneentitytwo" relationship. Found 0 related "Entityone".            There should be 1 "entityone". var objsettwo = context.            Entitytwos;            Objsettwo.mergeoption = mergeoption.notracking;            Objsettwo.addobject (New Entitytwo () {ID = 2, T1 = "Tt1", T2 = "Tt2", T3 = "tt3"}); Context.           SaveChanges (); The third case: sometimes our entitytwo may have been created before, and this is just a query to assign a value to the associated attribute when a new entityone is needed: entitytwo, but still reportedWrong: The relationship in the "Entityoneentitytwo" AssociationSet is in the "Deleted" state.           If there are multiple constraints, then the corresponding "Entityone" must also be in the "Deleted" state. var objsettwo = context.            Entitytwos;            var entitytwo = Objsettwo.single (t=>t.id==2); var Objsetone = context.            Entityones;            Objsetone.mergeoption = mergeoption.notracking;            Objsetone.addobject (New Entityone () {ID = 3, P1 = "Pp1", P2 = "Pp2", P3 = "PP3", Entitytwo = Entitytwo}); Context.        SaveChanges (); }

There is only one situation in which new additions can be performed correctly, as follows:

Model1container context = new Model1container ();            var Objsetone = context. Entityones;            Objsetone.addobject (New Entityone () {ID = 2, P1 = "Pp1", P2 = "Pp2", P3 = "PP3", Entitytwo = new Entitytwo () {id=2, T1 = "Tt1", T2 = "Tt2", T3 = "tt3"});            Context. SaveChanges ();

Note that you can only succeed if you complete the new Entityone and associated attribute entitytwo at the same time, but is this the reality? For example: A person has written a few books, it must be someone this entity, and then there will be a book this entity, each writing a book, the author of the book Association attribute should be a person this entity, but according to the above test, add a book must add a person, this is obviously wrong, how to solve it? I do not find a better solution at the moment, the only way is not to navigate, but this is not in line with the principle of object-oriented, so please give us a lot of advice, thank you!

Entity framework want to say love you not easy, so many error, so many limitations, how to solve?