What is the best way to enforce a child entity to be unique? For instance, lets say I have a Customer entity and a child entity collection called MarketingCampaign
public class Customer
{
public int ID { get; set; }
public virtual ICollection<MarketingCampaign> MarketingCampaigns { get; set; }
}
public class MarketingCampaign
{
public int ID { get; set; }
public string Name { get; set; }
}
Lets say that if a customer has the same MarketingCampaign added twice then it would be very bad as they would receive duplicate material.
In my code I could check if it exists before adding it but that relies on everyone knowing it must be unique.
Is there a way to force this on the model (preferably with data annotations)?
You are looking for a one-to-zero-or-one relationship.
You can indeed use DataAnnotations to accomplish what you're trying to do, but you should have an intermediary table that tracks the customer / campaign relationship and has a FK back to a Campaign table. Then with the magic of Entity Framework, it CustomerMarketingCampaignId will be both the PK of CustomerMarketingCampaign and FK back to Customer
public class Customer
{
public int CustomerId { get; set; }
public virtual ICollection<CustomerMarketingCampaign> CustomerMarketingCampaign { get; set; }
}
public class CustomerMarketingCampaign
{
[ForeignKey("Customer")]
public int CustomerMarketingCampaignId
[ForeignKey("Campaign")]
public int CampaignId { get; set; }
}
public class Campaign
{
public int CampaignId {get;set;}
public string Name {get;set;}
}
My final solution for posterity:
public class Customer
{
public int ID { get; set; }
public string Name { get; set; }
public virtual ICollection<CustomerMarketingCampaign> CustomerMarketingCampaigns { get; set; }
}
public class MarketingAction
{
public int ID { get; set; }
public string Name { get; set; }
}
public class CustomerMarketingCampaign
{
public int ID { get; set; }
[Index("IX_CustomerAndMarketing", 1, IsUnique = true)]
public int CustomerID { get; set; }
[Index("IX_CustomerAndMarketing", 2, IsUnique = true)]
public int MarketingActionID { get; set; }
// I also have several properties not included for tracking the progress of the campaign
[ForeignKey("CustomerID")]
public virtual Customer Customer { get; set; }
[ForeignKey("MarketingActionID")]
public virtual MarketingAction MarketingAction { get; set; }
}
Related
I'm working on a trucking API using Entity Framework (EF) Core. Basic CRUD operations are working fine using the repository pattern. There is an error in
configurations I am implementing, however.
I want to obtain multiple trailers and trucks associated with single load, reflecting the one-to-many relationship.
public class LoadConfiguration : IEntityTypeConfiguration<Load>
{
public void Configure(Microsoft.EntityFrameworkCore.Metadata.Builders.EntityTypeBuilder<Load> builder)
{
builder.Property(p=>p.Id).IsRequired();
builder.HasOne(t=>t.Customer).WithMany().HasForeignKey(p=>p.CustomerId);
builder.Property(p=>p.LoadedFrom).IsRequired();
builder.HasMany(p=>p.Trailer).WithOne().HasForeignKey(t=>t.TrailerId);
builder.HasMany(p=>p.Truck).WithOne().HasForeignKey(t=>t.TruckId);
builder.Property(p=>p.Destination).IsRequired();
}
}
public class Truck:BaseEntity
{
public int PlateNo { get; set; }
public string ModelName { get; set; }
public Location StateCode { get; set; }
public int PollutionCertificateValidity { get; set; }
public int DateOfPurchase { get; set; }
public int FitnessCertificateValidity { get; set; }
}
public class Load:BaseEntity
{
public Customer Customer { get; set; }
public int CustomerId { get; set; }
public string LoadedFrom { get; set; }
public Trailer Trailer { get; set; }
public int TrailerId { get; set; }
public Truck Truck { get; set; }
public int TruckId { get; set; }
public string Destination { get; set; }
}
public class Trailer:BaseEntity
{
public int TrailerCapacity { get; set; }
public Truck Truck { get; set; }
public int TruckId { get; set; }
}
public class BaseEntity
{
public int Id { get; set; }
}
A one-to-many relationship is defined by using navigation collections, that has the capacity to hold many Trucks and Trailers. You can choose the collection type freely, but I would suggest ICollection generic type.
Modify your Load class as follows:
public class Load:BaseEntity
{
public Customer Customer { get; set; }
public int CustomerId { get; set; }
public string LoadedFrom { get; set; }
public string Destination { get; set; }
// navigation collections
public ICollection<Trailer> Trailers { get; set; }
public ICollection<Truck> Trucks { get; set; }
}
You will then be able to set up the relationship in your LoadConfiguration class by using
the pluralized name:
builder.HasMany(p=>p.Trailers).WithOne();
builder.HasMany(p=>p.Trucks).WithOne();
.. even though EF Core will be smart enough to figure out the relation by convention so the fluent configuration is redundant.
I'm studying EF6 and think I know quite a bit already, but couldn't find a good solution (yet) for this:
Suppose I have the following model classes:
class LivingRoom {
public int Id { get; set; }
public string Name { get; set; }
public PersonTypeId { get; set; }
public IList<Person> Persons { get; set; }
}
class Person {
public int Id { get; set; }
public int PersonTypeId { get; set; }
public string Name { get; set; }
}
With these model classes I'm able to save and load via DbContext without any problem. Thanks to the navigation property in the "parent" LivingRoom class, the Persons collection will be included in this process. I don't have to load/save them separately.
UPDATE: Forgot the logical PersonTypeId field which will be used for determining which Persons should be in the collection property.
So far so good.
But EF6 is creating a FK in the Persons table, pointing to the LivingRooms table, which seems logical.
But what if I'm going to use the Persons table for a lot more other parent entities, like eg. "Bus" and "Plane", and therefore don't want to have a dependency (= FK field in LivingRooms table) in the Persons table?
Can I achieve this (don't create the FK field) without breaking the "include child list" load/save process as described?
If yes, how? And if no, why not?
NB: Please understand that I want to learn the best techniques. So good advice, to not doing this, is also welcome.
First , it's better to handle FK in Person Table ourself to do that web have this :
class LivingRoom
{
public int Id { get; set; }
public string Name { get; set; }
public IList<Person> Persons { get; set; }
}
class Person
{
public int Id { get; set; }
public string Name { get; set; }
public LivingRoom LivingRoom { get; set; }
public int LivingRoomId { get; set; }
}
now If you have others Entities Like Bus and ... so we have
public class Bus
{
public int Id { get; set; }
public ICollection<Person> People { get; set; }
}
and Updated Person class is :
public class Person
{
public int Id { get; set; }
public string Name { get; set; }
public LivingRoom LivingRoom { get; set; }
public int LivingRoomId { get; set; }
public Bus Bus{ get; set; }
public int BusId { get; set; }
}
you can set FK in Person Table as Nullable to do this :
public class Person
{
public int Id { get; set; }
public string Name { get; set; }
public LivingRoom LivingRoom { get; set; }
public int? LivingRoomId { get; set; }
public Bus Bus{ get; set; }
public int? BusId { get; set; }
}
As you can see We set BusId and LivingRoomId as nullable or you can just set one of them that you want
Note : You need to add some mapper to tell EF which field id FK and something like this ,...
My data class is
public class Data
{
public int Id { get; set; }
public int LeagueId { get; set; }
public League League { get; set; }
public int HomeTeamId { get; set; }
public virtual Team HomeTeam { get; set; }
public int AwayTeamId { get; set; }
public virtual Team AwayTeam { get; set; }
}
and my team class is
public class Team
{
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Data> Datas { get; set; }
}
which generates an extra foreign key FK_dbo.Data_dbo.Teams_Team_Id and also and extra column in my Data table.
So my first question is, how that foreign-key was created there?
Can i have two one to many relationships that target at the same table with entity framework?
I need to set both the HomeTeamId and the AwayTeamId in the Data table as one to many relationship
Try:
public class Data
{
public int Id { get; set; }
public int LeagueId { get; set; }
[ForeignKey("LeagueId")] /* Add explicit foreign key data annotations */
public League League { get; set; }
public int HomeTeamId { get; set; }
[ForeignKey("HomeTeamId")]
public virtual Team HomeTeam { get; set; }
public int AwayTeamId { get; set; }
[ForeignKey("AwayTeamId")]
public virtual Team AwayTeam { get; set; }
}
public class Team
{
public Team()
{
this.HomeTeamData = new HashSet<Data>();
this.AwayTeamData = new HashSet<Data>();
}
public int Id { get; set; }
public string Name { get; set; }
[InverseProperty("HomeTeam")]
public virtual ICollection<Data> HomeTeamData { get; set; }
[InverseProperty("AwayTeam")]
public virtual ICollection<Data> AwayTeamData { get; set; }
}
Let me know if this helps.
I suspect you may be hitting the limit of Entity's ability to figure out what you want. You may need to consider using some Entity Annotations to instruct Entity on what you want it to actually do.
I'm trying to define a relationship between 2 tables with the ForeignKeyAttribute.
I came a cross a few sites that described an interesting method of doing this with the ForeignKeyAttribute.
Here are the two code samples:
The first one:
public class Customer
{
public int ID { get; set; }
public int OrderID { get; set; }
// Some other properties
[ForeignKey("OrderID")]
public virtual Order Order { get; set; }
}
public class Order
{
public int ID { get; set; }
public int CustomerID { get; set; }
// Some other properties
[ForeignKey("CustomerID")]
public virtual Customer Customer { get; set; }
}
The second one:
public class Customer
{
public int ID { get; set; }
[ForeignKey("Order")]
public int OrderID { get; set; }
// Some other properties
public virtual Order Order { get; set; }
}
public class Order
{
public int ID { get; set; }
[ForeignKey("Customer")]
public int CustomerID { get; set; }
// Some other properties
public virtual Customer Customer { get; set; }
}
In the first code sample, the ForeignKeyAttribute is placed on the public virtual Customer Customer { get; set; }.
And in the second code sample on the public int CustomerID { get; set; } (Order- and CustomerID).
My question is, how do I know which method to use in which situation?
I know this could be done too using Fluent API, but that's irrelevant at the moment for this question.
First, just want to say that you do not need to place the ForeignKey attribute on any property. Simply doing the following should be enough:
public class Customer
{
public int ID { get; set; }
//EF will create the relationship since the property is named class+id
//the following is not necessary, is just good practice
//if this is omitted EF will create a Order_Id on its own
public int OrderID { get; set; }
// Some other properties
public virtual Order Order { get; set; }
}
public class Order
{
public int ID { get; set; }
// no need to include the id property
// Some other properties
public virtual Customer Customer { get; set; }
}
Having said that, the answer is that the ForeignKey construct takes in a string parameter. If you place it on the foreign key property it should have the name of the navigation property, if you place it on the navigation property it should have the name of the foreign key. Where you place it is completely up to you, as long as you keep in mind what string value to use.
This will create two tables "Ingredient" and "Recipe" and an additional table for many-to-many mapping.
public class DC : DbContext {
public DbSet<Ingredient> Ingredients { get; set; }
public DbSet<Recipe> Recipes { get; set; }
}
public class Ingredient {
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Recipe> Recipes { get; set; }
}
public class Recipe {
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<Ingredient> Ingredients { get; set; }
}
Question: I want to include additional column "quantity" in the third mapping table that will be created by Entity Framework. How to make that possible? Thanks in advance.
When you've got some extra information, I suspect it won't really count as a mapping table any more - it's not just a many-to-many mapping. I think you should just model it as another table:
public class Ingredient {
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<RecipePart> RecipeParts { get; set; }
}
public class RecipePart {
public int Id { get; set; }
public Ingredient { get; set; }
public Recipe { get; set; }
// You'll want to think what unit this is meant to be in... another field?
public decimal Quantity { get; set; }
}
public class Recipe {
public int Id { get; set; }
public string Name { get; set; }
public virtual ICollection<RecipePart> Parts { get; set; }
}
So now you don't really have a many-to-many mapping - you have two ordinary many-to-one mappings. Do you definitely need to "ingredient to recipes" mapping exposed in your model at all? If you want to find out all the recipes which use a particular ingredient, you could always do a query such as:
var recipies = DB.Recipies.Where(r => r.Parts
.Any(p => p.Ingredient == ingredient));