Entity Framework Configuring relationships with the Fluent API

RELATED links: Configuring relationships with the Fluent API

Configuring a required-to-optional relationship (One-to-zero-or-one 1 ... 0,1)

The following example, which represents 1 ... 0,1 's relationship. The OfficeAssignment table has an attribute Instructorid, which is a primary key and also a foreign key.

The Haskey method is used to configure the primary key.

modelbuilder.entity<officeassignment> ()     = t.instructorid);    //  modelbuilder.entity<officeassignment>()     = t.instructor)     and T. OfficeAssignment);

Configuring a Relationship Where Both Ends is Required (one-to-one)

modelbuilder.entity<officeassignment> ()     = T.instructorid);    Modelbuilder.entity<Instructor>()     = t.officeassignment)     and T. Instructor);

Configuring a Many-to-many Relationship

Modelbuilder.entity<course>()     = t.instructors)     = t.courses)

Modelbuilder.entity<course>()     = t.instructors)     = t.courses)     = =     {         m.totable ("courseinstructor");         M.mapleftkey ("courseid");         M.maprightkey ("instructorid");     });

Configuring a relationship with one Navigation property

modelbuilder.entity<officeassignment> ()     = T.instructorid);    Modelbuilder.entity<Instructor>()     = t.officeassignment)     . Withrequiredprincipal ();

Enabling Cascade Delete

Modelbuilder.entity<course>()     = t.department)     = t.courses)      = d.departmentid)     . Willcascadeondelete (false);

Configuring a Composite Foreign Key

modelbuilder.entity<department>New  {d.departmentid, d.name});    //  modelbuilder.entity<course>()      = c.department)      and D. Courses)     new {d.departmentid, d.departmentname});

Renaming a Foreign Key that's not Defined in the Model

Modelbuilder.entity<course>()     = c.department)     = t.courses)      = = M.mapkey ("changeddepartmentid"));

Configuring a Foreign Key Name that Does not follow the Code first convention

Modelbuilder.entity<course>()          = c.department)          = d.courses)           = C.somedepartmentid);

Model used in Samples

usingSystem.Data.Entity;usingSystem.Data.Entity.ModelConfiguration.Conventions;//add a reference to System.ComponentModel.DataAnnotations DLLusingSystem.ComponentModel.DataAnnotations;usingSystem.Collections.Generic;usingSystem;  Public classSchoolentities:dbcontext { PublicDbset<course> Courses {Get;Set; }  PublicDbset<department> Departments {Get;Set; }  PublicDbset<instructor> Instructors {Get;Set; }  PublicDbset<officeassignment> officeassignments {Get;Set; } protected Override voidonmodelcreating (Dbmodelbuilder modelBuilder) {//Configure Code First to ignore Pluralizingtablename convention//If You keep this convention then the generated tables would have pluralized names.Modelbuilder.conventions.remove<pluralizingtablenameconvention>(); } }   Public classDepartment { PublicDepartment () { This. Courses =NewHashset<course>(); }     //Primary Key     Public intDepartmentID {Get;Set; }  Public stringName {Get;Set; }  Public decimalBudget {Get;Set; }  PublicSystem.DateTime StartDate {Get;Set; }  Public int? Administrator {Get;Set; } //Navigation Property     Public VirtualIcollection<course> Courses {Get;Private Set; } }   Public classCourse { PublicCourse () { This. Instructors =NewHashset<instructor>(); }     //Primary Key     Public intCourseID {Get;Set; }  Public stringTitle {Get;Set; }  Public intCredits {Get;Set; } //Foreign Key     Public intDepartmentID {Get;Set; } //Navigation Properties     Public VirtualDepartment Department {Get;Set; }  Public VirtualIcollection<instructor> Instructors {Get;Private Set; } }   Public Partial classOnlinecourse:course { Public stringURL {Get;Set; } }   Public Partial classOnsitecourse:course { PublicOnsiteCourse () {Details=NewDetails (); }       PublicDetails (Details) {Get;Set; } }   Public classDetails { PublicSystem.DateTime Time {Get;Set; }  Public stringLocation {Get;Set; }  Public stringDays {Get;Set; } }       Public classInstructor { PublicInstructor () { This. Courses =NewList<course>(); }      //Primary Key     Public intInstructorid {Get;Set; }  Public stringLastName {Get;Set; }  Public stringFirstName {Get;Set; }  PublicSystem.DateTime HireDate {Get;Set; } //Navigation Properties     Public VirtualIcollection<course> Courses {Get;Private Set; } }   Public classOfficeAssignment {//specifying Instructorid as a primary[Key ()] PublicInt32 Instructorid {Get;Set; }  Public stringLocation {Get;Set; } //When the Entity Framework sees Timestamp attribute//it configures Concurrencycheck and databasegeneratedpattern=computed.1537884940 PublicByte[] Timestamp {Get;Set; } //Navigation Property     Public VirtualInstructor Instructor {Get;Set; } }

Entity Framework Configuring relationships with the Fluent API