Many-to-many relations of entityframework (IV.)

The previous article describes a one-to-many relationship, the following describes the next many-to-many relationship code writing.

1, the new model entity, user is the users class, role is a character class, because it is a many-to-many relationship, there must be an intermediate class, so produced the Userrole class

1      Public classUser2     {3          Public intId {Get;Set; }4          Public stringName {Get;Set; }5 6          Public VirtualIcollection<userrole> Userroles {Set;Get; }7     }8 9      Public classRoleTen     { One          Public intId {Get;Set; } A          Public stringName {Get;Set; } -  -          Public VirtualIcollection<userrole> Userroles {Set;Get; } the     } -  -      Public classuserrole -     { +          Public intId {Get;Set; } -          Public intUId {Get;Set; } +          Public intRId {Get;Set; } A  at          Public VirtualUser User {Set;Get; } -          Public VirtualRole role {Set;Get; } -}

2. Create a entitycontext and inherit from DbContext

1      Public classEntitycontext:dbcontext2     {3          PublicEntitycontext ()4:Base("name=dbconnectionstring")5         {6 7         }8 9          PublicDbset<user> User {Get;Set; }Ten          PublicDbset<role> Role {Get;Set; } One          PublicDbset<userrole> Userrole {Get;Set; } A  -         protected Override voidonmodelcreating (Dbmodelbuilder modelBuilder) -         { the modelBuilder.Configurations.AddFromAssembly (assembly.getexecutingassembly ()); -             Base. Onmodelcreating (ModelBuilder); -         } -}

3. Add the database connection string in the Web. config file

1   < connectionStrings > 2     <  name= "dbconnectionstring"  connectionString= "Data source=.;i Nitial catalog=manytomany;integrated security=true "  providerName=" System.Data.SqlClient "  />3   </connectionStrings>

4. Then create the Entity mappings

1      Public classUsermap:entitytypeconfiguration<user>2     {3          PublicUserMap ()4         {5ToTable ("User");6Haskey (U =u.id);7         }8     }9 Ten      Public classRolemap:entitytypeconfiguration<role> One     { A          PublicRolemap () -         { -ToTable ("Role"); theHaskey (R =r.id); -         } -     } -  +      Public classUserrolemap:entitytypeconfiguration<userrole> -     { +          PublicUserrolemap () A         { atToTable ("userrole"); -Haskey (ur =Ur. ID); -  -             //Willcascadeondelete: Do not use cascade delete -Hasrequired (pt = pt. User). Withmany (p = p.userroles). Hasforeignkey (pt = pt. UID). Willcascadeondelete (false); -  inHasrequired (pt = pt. Role). Withmany (t = t.userroles). Hasforeignkey (pt = pt. RID). Willcascadeondelete (false); -         } to}

5, we write some operations, let code first build the database and verify that the data is new

1     varuser =NewUser () {Name ="Bob" };2Db. Set<user>(). ADD (user);3 4     varRole =NewRole () {Name ="Admin" };5Db. Set<role>(). ADD (role);6 7 db. SaveChanges ();8 9     varur =NewUserrole () {RId = role. Id, UId =user. ID};TenDb. Set<userrole>(). ADD (UR); One db. SaveChanges (); A  -     //var list = db. Set<user> (). Include ("Userroles"). ToList (); -     //If you need to find out what role userroles under, the     //avoid the need to access the database through lazy loading (the same foreign key entity will only be accessed once, but more still in the following ways) -     varList = db. Set<user> (). Include ("Userroles.role"). ToList ();

6. Database diagram

Many-to-many relations of entityframework (IV.)