A SchoolclassCode can have many Pupils.
A Pupil can belong to many SchoolclassCodes.
This is an N to M relation.
I thought N to M relation work in code first by default.
But I also explicitly create the N to M relation here:
modelBuilder.Entity<SchoolclassCode>().
HasMany(c => c.Pupils).
WithMany(p => p.SchoolclassCodes).
Map(
m =>
{
m.MapLeftKey("SchoolclassCodeId");
m.MapRightKey("PupilId");
m.ToTable("SchoolclassCodePupil");
});
public class SchoolclassCode
{
public SchoolclassCode()
{
Pupils = new HashSet<Pupil>();
Tests = new HashSet<Test>();
}
public int Id { get; set; }
public string SchoolclassCodeName { get; set; }
public string SubjectName { get; set; }
public int Color { get; set; }
public string ClassIdentifier { get; set; }
public ISet<Pupil> Pupils { get; set; }
public ISet<Test> Tests { get; set; }
public Schoolyear Schoolyear { get; set; }
public int SchoolyearId { get; set; }
}
public class Pupil
{
public Pupil()
{
PupilsTests = new HashSet<PupilTest>();
SchoolclassCodes = new HashSet<SchoolclassCode>();
}
public int Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string Postal { get; set; }
public string City { get; set; }
public string Street { get; set; }
public ISet<PupilTest> PupilsTests { get; set; }
public ISet<SchoolclassCode> SchoolclassCodes { get; set; }
}
On the Pupil Table no foreign key is created at all, Why this?
For a many to many relationship, there is no foreign key on either side. The foreign keys are on the join table, which you have mapped to the table SchoolclassCodePupil:
modelBuilder.Entity<SchoolclassCode>().
HasMany(c => c.Pupils).
WithMany(p => p.SchoolclassCodes).
Map(m =>
{
m.MapLeftKey("SchoolclassCodeId");
m.MapRightKey("PupilId");
m.ToTable("SchoolclassCodePupil");
});
Entity Framework uses that junction table to determine what belongs in the somePupil.SchoolclassCodes set.
Related
Am Trying to create Two Tables like bellow got some EF error.
public class Student : ModelsBase
{
public string AdharNumber { get; set; }
public byte Religion { get; set; }
public int CategoryID { get; set; }
public string Cast { get; set; }
public string SubCast { get; set; }
public string Photo { get; set; }
public DateTime DateOfJoining { get; set; } = DateTime.Now;
[Required]
public ICollection<Address> TemporaryAddress { get; set; }
[Required]
public ICollection<Address> PermanentAddress { get; set; }
}
public class Address : ModelsBase
{
public string DoorNo { get; set; }
public string StreetLocality { get; set; }
public string Landmark { get; set; }
public string City { get; set; }
public int Taluk { get; set; }
public int District { get; set; }
public int State { get; set; }
public string Pincode { get; set; }
public bool IsPermanent { get; set; } = true;
public bool IsDefault { get; set; } = true;
[ForeignKey("Student")]
public Guid StudentId { get; set; }
}
Getting the bellow error while trying to Run the "Add-Migration command"
Both relationships between 'Address' and 'Student.PermanentAddress' and between 'Address' and 'Student.TemporaryAddress' could use {'StudentId'} as the foreign key. To resolve this, configure the foreign key properties explicitly in 'OnModelCreating' on at least one of the relationships
Please help. Thanks!
Your issue is that from the Address side of things you have a Many-to-1 with a single Student, but from the Student side of things you want 2x 1-to-Many relationships.
Since The relationship is really just a 1-to-Many from the student that you want to discriminate between temporary and permanent addresses:
public class Student : ModelsBase
{
public string AdharNumber { get; set; }
public byte Religion { get; set; }
public int CategoryID { get; set; }
public string Cast { get; set; }
public string SubCast { get; set; }
public string Photo { get; set; }
public DateTime DateOfJoining { get; set; } = DateTime.Now;
[Required]
public ICollection<Address> Addresses { get; set; } = new List<Address>();
[NotMapped]
public ICollection<Address> TemporaryAddresses => Addresses.Where(x => !x.IsPermanent).ToList();
[NotMapped]
public ICollection<Address> PermanentAddresses => Addresses.Where(x => x.IsPermanent).ToList();
}
With 1-to-many collections I recommend initializing them to an empty list to avoid null reference exceptions especially if lazy loading is disabled.
The caveat here is that from EF's perspective, Student only has the Addresses collection, do not attempt to use either TemporaryAddresses or PermanentAddresses in a query expression as these are unmapped accessors. If you want to filter based on a permanent address you will have to do it through Addresses and include the condition on IsPermanent in the query.
For example:
// Not valid...
var studentsInDetroit = context.Students.Where(x => x.PermanentAddresses.Any(a => a.City == "Detroit")).ToList();
// Valid...
var studentsInDetroit = context.Students.Where(x => x.Addresses.Any(a => a.IsPermanent && a.City == "Detroit")).ToList();
Normally I don't recommend using unmapped accessors in entities because of this. It is generally better to leave entities representing pure domain/data state and project that down to view models which can be more concerned about splitting the data into a more palatable form for consumption.
I have to apply a set of relationships with a system that incorporates a messaging system.
I have the two of my domain object with one mapping object (for the many-to-many relationship):
public class User
{
public User()
{
UserMails = new List<UserMail>();
}
public int Id { get; set; }
public ICollection<UserMail> UserMails { get; set; }
}
public class Mail
{
public Mail()
{
UserMails = new List<UserMail>();
}
public int Id { get; set; }
public string Title { get; set; }
public string Body { get; set; }
public ICollection<UserMail> UserMails { get; set; }
}
public class UserMail
{
public int Id { get; set; }
public int FromUserId { get; set; }
public User FromUser { get; set; }
public int ToUserId { get; set; }
public User ToUser { get; set; }
public int MailId { get; set; }
public Mail Mail { get; set; }
}
How would I configure this relationship using Fluent API such that there's a many to many relationship between User and Mail and Mail can have 2 foreign keys back to the UserFrom and UserTo?
Any help on this would be greatly appreciated.
If you are trying to model the relationship between a mail and its sender/recipient, then you don't need a many-to-many relation, or 2 foreign keys in your joining entity. Instead, you need 2 one-to-many relations like below -
public class User
{
public int Id { get; set; }
public string Name { get; set; }
public ICollection<Mail> ReceivedMails { get; set; }
public ICollection<Mail> SentMails { get; set; }
}
public class Mail
{
public int Id { get; set; }
public string Title { get; set; }
public string Body { get; set; }
public int SenderId { get; set; }
public User Sender { get; set; }
public int RecipientId { get; set; }
public User Recipient { get; set; }
}
and you can configure them as -
protected override void OnModelCreating(ModelBuilder builder)
{
builder.Entity<Mail>()
.HasOne(p => p.Sender)
.WithMany(p => p.SentMails)
.HasForeignKey(p => p.SenderId)
.OnDelete(DeleteBehavior.NoAction);
builder.Entity<Mail>()
.HasOne(p => p.Recipient)
.WithMany(p => p.ReceivedMails)
.HasForeignKey(p => p.RecipientId)
.OnDelete(DeleteBehavior.NoAction);
}
public class Report
{
[Key]
public int ReportId { get; set; }
[ForeignKey("Subjects")]
public int SubjectId { get; set; }
public Subjects Subjects { get; set; }
[ForeignKey("Teacher")]
public int TeacherId { get; set; }
public Teacher Teacher { get; set; }
[ForeignKey("MarkType")]
public int MarkTypeId { get; set; }
public MarkType MarkType { get; set; }
}
public class Teacher
{
[Key]
public int TeacherId { get; set; }
[MaxLength(50)]
[Required]
public string FName { get; set; }
[MaxLength(50)]
[Required]
public string LName { get; set; }
}
public class Student
{
[Key]
public int StudentId { get; set; }
[MaxLength(50)]
[Required]
public string FName { get; set; }
[MaxLength(50)]
[Required]
public string LName { get; set; }
[ForeignKey("Grade")]
public int GradeId { get; set; }
public Grade Grade { get; set; }
}
public class Grade
{
[Key]
public int GradeId { get; set; }
public int StudentGrade { get; set; }
}
public class Subjects
{
[Key]
public int SubjectId { get; set; }
[MaxLength(50)]
[Required]
public string SubjectName { get; set; }
}
public class Terms
{
[Key]
public int TermId { get; set; }
public int Term { get; set; }
}
public class MarkType
{
[Key]
public int MarkTypeId { get; set; }
[MaxLength(20)]
[Required]
public string TypeName { get; set; }
}
public class StudentMark
{
[Key]
public int StudentMarkId { get; set; }
[ForeignKey("Report")]
public int ReportId { get; set; }
public Report Report { get; set; }
[ForeignKey("Student")]
public int StudentId { get; set; }
public Student Student { get; set; }
public int Mark { get; set; }
[ForeignKey("Terms")]
public int TermId { get; set; }
public Terms Terms { get; set; }
}
In the API I am making I want to have the ability to use two different IDs to get a more specific response.
var report = ReportDBContext.StudentMark
.Include(p => p.Student.Grade).Include(p => p.Report)
.Include(p => p.Terms).Include(a => a.Report.Subjects).Include(a => a.Terms)
.Include(a => a.Report.MarkType).Include(a => a.Report.Teacher).ToList();
This allowed me to get StudentMark as well as it's related entities but I want to have the ability to use The student's Id and the Term's Id to get a student's marks for that term and all the subjects related to the student. I am a beginner to Web API so please let me know if I need to add more context.
If you want to query by either StudentId or TermId, I suggest that you provide two different endpoints for these two different queries. Use LINQ Where to check your conditions.
public StudentMark[] GetMarksByStudentId(int studentId) {
return ReportDBContext.StudentMark
/* .Include(...) */
.Where(mark => mark.StudentId == studentId)
.ToArray();
}
public StudentMark[] GetMarksByTermId(int termId) {
return ReportDBContext.StudentMark
/* .Include(...) */
.Where(mark => mark.TermId == termId)
.ToArray();
}
If you want to query by StudentId and TermId simultaneously, introduce a query object to encapsulate your parameters. You can test for multiple conditions in the Where clause with AND &&.
public StudentMark[] FindMarks(StudentMarkQuery query) {
return ReportDBContext.StudentMark
/* .Include(...) */
.Where(mark => mark.StudentId == query.StudentId
&& mark.TermId == query.TermId)
.ToArray();
}
The StudentMarkQuery class is introduced so you can add additional parameters without changing the overall signature of the endpoint:
public class StudentMarkQuery {
public int StudentId { get; set; }
public int TermId { get; set; }
}
Hi I have the three classes below. I'm trying achieve a many to many mapping with three classes. I have achieved many to many relationship between two classes but I'm trying to get another class in the mix. Below is the classes I have and a class representation of the relationship I'm trying to achieve.
public class Person
{
public int ID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string EmployeeId { get; set; }
public ICollection<Department> Departments { get; set; }
}
public class Department
{
public int ID { get; set; }
public string Name { get; set; }
public string DepartmentCode { get; set; }
public string Description { get; set; }
public ICollection<Person> Members { get; set; }
}
public class Role
{
public int ID { get; set; }
public string Name { get; set; }
public string Description { get; set; }
}
Any hints on how to achieve the below would be helpful.
public class PersonRoleDepartment
{
public int PersonID { get; set; }
public int DepartmentID{ get; set; }
public int RoleID { get; set; }
}
public class Person
{
public int Id { get; set; }
public ICollection<PersonDepartmentRole> DepartmentRoles { get; set; }
}
public class Department
{
public int Id { get; set; }
public ICollection<PersonDepartmentRole> PersonRoles { get; set; }
}
public class Role
{
public int Id { get; set; }
public ICollection<PersonDepartmentRole> PersonDepartments { get; set; }
}
public class PersonDepartmentRole
{
[Key, Column( Order = 0 )]
public int PersonId { get; set; }
[ForeignKey( "PersonId" )]
[Required]
public virtual Person Person { get; set; }
[Key, Column( Order = 1 )]
public int DepartmentId { get; set; }
[ForeignKey( "DepartmentId" )]
[Required]
public virtual Department Department { get; set; }
[Key, Column( Order = 2 )]
public int RoleId { get; set; }
[ForeignKey( "RoleId" )]
[Required]
public virtual Role Role { get; set; }
}
Fluent API config:
var pdrConfig = modelBuilder.Entity<PersonDepartmentRole>()
.HasKey( pdr => new
{
pdr.PersonId,
pdr.DepartmentId,
pdr.RoleId
} );
pdrConfig.HasRequired( pdr => pdr.Department )
.WithMany( d => d.PersonRoles )
.HasForeignKey( pdr => pdr.DepartmentId );
pdrConfig.HasRequired( pdr => pdr.Person )
.WithMany( p => p.DepartmentRoles )
.HasForeignKey( pdr => pdr.PersonId );
pdrConfig.HasRequired( pdr => pdr.Role )
.WithMany( r => r.PersonDepartments )
.HasForeignKey( pdr => pdr.RoleId );
Note: all references from any of the primary entities to the others should route through your junction entity PersonDepartmentRole - if not, data inconsistencies can arise (e.g. I add a Department to a Person as well as a corresponding PersonDepartmentRole record to the DB, but then I remove the Department from the Person entity - the PersonDepartmentRole entity still remains)
Instead, if you want all departments for a person:
db.Person.DepartmentRoles.Select( dr => dr.Department ).Distinct()
In this construct, can a person be in a department but have no role? Or, can a department play a role but has no people? If not, how could this be accomplished
I have the following tables Essence, EssenseSet, and Essense2EssenceSet
Essense2EssenceSet is the linking table that creates the M:M relationship.
I've been unable to get the M:M relationship working though in EF code first though.
Here's my code:
[Table("Essence", Schema = "Com")]
public class Essence
{
public int EssenceID { get; set; }
public string Name { get; set; }
public int EssenceTypeID { get; set; }
public string DescLong { get; set; }
public string DescShort { get; set; }
public virtual ICollection<EssenceSet> EssenceSets { get; set; }
public virtual EssenceType EssenceType { get; set; }
}
[Table("EssenceSet", Schema = "Com")]
public class EssenceSet
{
public int EssenceSetID { get; set; }
public int EssenceMakerID { get; set; }
public string Name { get; set; }
public string DescLong { get; set; }
public string DescShort { get; set; }
public virtual ICollection<Essence> Essences { get; set; }
}
[Table("Essence2EssenceSet", Schema = "Com")]
public class Essence2EssenceSet
{
//(PK / FK)
[Key] [Column(Order = 0)] [ForeignKey("Essence")] public int EssenceID { get; set; }
[Key] [Column(Order = 1)] [ForeignKey("EssenceSet")] public int EssenceSetID { get; set; }
//Navigation
public virtual Essence Essence { get; set; }
public virtual EssenceSet EssenceSet { get; set; }
}
public class EssenceContext : DbContext
{
public DbSet<Essence> Essences { get; set; }
public DbSet<EssenceSet> EssenceSets { get; set; }
public DbSet<Essence2EssenceSet> Essence2EssenceSets { get; set; }
protected override void OnModelCreating(DbModelBuilder mb)
{
mb.Entity<Essence>()
.HasMany(e => e.EssenceSets)
.WithMany(set => set.Essences)
.Map(mc =>
{
mc.ToTable("Essence2EssenceSet");
mc.MapLeftKey("EssenceID");
mc.MapRightKey("EssenceSetID");
});
}
}
This is the code I'm trying to run:
Essence e = new Essence();
e.EssenceTypeID = (int)(double)dr[1];
e.Name = dr[2].ToString();
e.DescLong = dr[3].ToString();
//Get Essence Set
int setID = (int)(double)dr[0];
var set = ctx.EssenceSets.Find(setID);
e.EssenceSets = new HashSet<EssenceSet>();
e.EssenceSets.Add(set);
ctx.Essences.Add(e);
ctx.SaveChanges();
And here's the error:
An error occurred while saving entities that do not expose foreign key properties for their relationships. The EntityEntries property will return null because a single entity cannot be identified as the source of the exception.
I'm not able to find the problem. I'd greatly appreciate help setting this up right.
Thanks!
Remove your Essence2EssenceSet model class. If junction table contains only keys of related entities participating in many-to-many relations it is not needed to map it as entity. Also make sure that your fluent mapping of many-to-many relations specifies schema for table:
mb.Entity<Essence>()
.HasMany(e => e.EssenceSets)
.WithMany(set => set.Essences)
.Map(mc =>
{
mc.ToTable("Essence2EssenceSet", "Com");
mc.MapLeftKey("EssenceID");
mc.MapRightKey("EssenceSetID");
});