I'm trying to create a little asset management application, like an inventory. There are asset types (like notebook, mobile phone, desk, dishwasher etc.) and assets (like notebook-001, mobile-010 etc.).
So this is my AssetType model:
public class AssetType
{
public int Id { get; set; }
public string Name { get; set; }
public ICollection<AssetTypeMeta> AssetTypeMetas { get; set; }
}
And this is my Asset model:
public class Asset
{
public int Id { get; set; }
[ForeignKey("TypeId")]
public AssetType AssetType { get; set; }
public int TypeId { get; set; }
public string SerialNumber { get; set; }
public double PurchasePrice { get; set; }
public ICollection<AssetMeta> FieldNames { get; set; }
public ICollection<AssetTypeMeta> FieldValues { get; set; }
}
As you can see, there are only 2 fields in my asset table, SerialNumber and PurchasePrice. But I want user to be able to define new fields specific to the device type and be able to enter information to those fields. When I test it in my database, everything looks fine.
For this I have created two more models. One of them is AssetTypeMeta, which is meant to hold new (user-defined) field names for the user.
public class AssetTypeMeta
{
public int Id { get; set; }
[ForeignKey("AssetTypeId")]
public AssetType AssetType { get; set; }
public int AssetTypeId { get; set; }
public string FieldName { get; set; }
}
And I've added a new model, AssetMeta, which is a link between an asset type, an asset and user defined fields for that asset type.
public class AssetMeta
{
public int Id { get; set; }
[ForeignKey("AssetTypeMetaId")]
public AssetTypeMeta AssetTypeMeta { get; set; }
public int AssetTypeMetaId { get; set; }
[ForeignKey("AssetId")]
public Asset Asset { get; set; }
public int AssetId { get; set; }
public string? FieldValue{ get; set; }
}
I can define fields like IMEI, NFC, Operator etc. for the device type "Mobile Phone" in AssetTypeMeta table and link them to the actual devices in AssetMeta table, like mobile-phone01's IMEI is 11111111111 and Operator is Vodafone etc.
But I can't make all those information visible in my page. For example, if a user clicks on the device mobile-phone01, I have to also show the user defined fields for that device, like IMEI and Operator (even if they don't have any values assigned in AssetMeta table).
How do I set up my viewmodel, action and view to do that?
Related
I'm trying to build a recipe app for my spouse. I'm trying to set it up so she can add new recipes to the database as the app grows.
When adding new recipe, she will have three drop-down to pick from to construct her new recipe ingredients. First one will contain a list of ingredients that she can choose from, the second one a list of measuring units and the third one a list of quantities.
Here is what I got so far. Am I heading in the right direction or am I off? I'm using Entity Framework with a code-first approach:
public class Recipes
{
public int Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public string Image { get; set; }
}
public class Units model
{
[Key]
public int Id { get; set; }
public string UnitName { get; set; }
}
public class UnitQty
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
}
public class IngredientsModel
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
}
public class RecipeIngredients
{
public int Id { get; set; }
public int RecipesId { get; set; }
[ForeignKey("RecipesId")]
public Recipes Recipes { get; set; }
public int IngredientsModelId { get; set; }
[ForeignKey("IngredientsModelId")]
public IngredientsModel IngredientsModel { get; set; }
public int UnitQtyId { get; set; }
[ForeignKey("UnitQtyId")]
public UnitQty UnitQty { get; set; }
public int UnitsModelId { get; set; }
[ForeignKey("UnitsModelId")]
public UnitsModel UnitsModel { get; set; }
}
After creating the table, controller and the views, this is what I get in the recipe ingredients index view.
Any suggestion will be more than welcome please and thank you
RecipeIngredient class's view
First of all. You are over engineering your domain model. On relational databases Join is bottleneck you should prevent from joins if it doesn't helps you.
public class Recipt
{
public int Id { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public string Image { get; set; }
public ICollection<RecipeIngredient> Ingredients { get; set; }
}
public class IngredientModel
{
public int Id { get; set; }
public string Name { get; set; }
public IngredientUnit UnitType { get; set; } // Unit model is best to be added here. if it doesn't change in a single IngredientModel.
}
public class RecipeIngredient
{
public int Id { get; set; }
public int UnitQuantiy { get; set; } // No need to more classes.
public IngredientModel Model { get; set; }
public Recipt Recipt { get; set; }
}
public Enum IngredientUnitType // Same Unit Model but less database relation as its small finite collection.
{
Killogram,
Count,
....
}
and according to the Microsoft documents its best to use fluentApi configuration for the relations.
Override this method in your Context:
protected override void OnModelCreating(ModelBuilder builder)
{
builder.Entity<Recipt>.HasMany(P => P.Ingredients).WithOne(P => P.Recipt);
builder.Entity<RecipeIngredient>.HasOne(P => P.Model);
// There is no need to explicit foreign key definition. but you can explicitly define your foreign keys.
}
And for the last part. in Views you can use extra models called ViewModels.
As above domain turned to a minimal domain you just need to pass a list of IngredientModels to your view to complete your View.
How can I generate above table like structure using Entity Framework core?
I am using code first approach to generate my tables from domain models which are as follows
public class Contact
{
public int ContactId { get; set; }
public string Email { get; set; }
public string Name { get; set; }
}
public class Company
{
public int CompanyId { get; set; }
public string CompanyName { get; set; }
[ForeignKey("Contact")]
public int FirstContact { get; set; }
[ForeignKey("Contact")]
public int SecondContact { get; set; }
[ForeignKey("Contact")]
public int ThirdContact { get; set; }
public virtual Contact Contact { get; set; }
}
In the company table, I want foreign key on columns 'FirstContact', 'SecondContact', 'ThirdContact' which can refer to Contacts table.
I have also tried Fluent API but no success in same also.
Whenever I am running the add-migration command, I am getting this error:
There are multiple properties with the [ForeignKey] attribute pointing to navigation 'Company.Contact'. To define a composite foreign key using data annotations, use the [ForeignKey] attribute on the navigation.
I would appreciate any help regarding the same.
Thanks.
For multiple Navigation Properties, you need multiple Foreign Keys. EG
public class Company
{
public int CompanyId { get; set; }
public string CompanyName { get; set; }
public virtual Contact FirstContact { get; set; }
public virtual Contact SecondContact { get; set; }
public virtual Contact ThirdContact { get; set; }
}
And let EF Core create shadow properties for your FKs or with Foreign Key properties:
public class Company
{
public int CompanyId { get; set; }
public string CompanyName { get; set; }
public int FirstCotactId {get; set;}
public virtual Contact FirstContact { get; set; }
public int SecondCotactId {get; set;}
public virtual Contact SecondContact { get; set; }
public int SecondCotactId {get; set;}
public virtual Contact ThirdContact { get; set; }
}
I am trying in .NET EFCore the following Code-First migrations through the entities below
User
[Table("Users")]
public class User
{
[Key]
public int Id { get; set; }
[Required]
[MaxLength(100)]
public string FirstName { get; set; }
[Required]
[MaxLength(100)]
public string LastName { get; set; }
[Required]
[MaxLength(250)]
public string Email { get; set; }
[Required]
[MinLength(8), MaxLength(16)]
public string Password { get; set; }
[Required]
[MinLength(6), MaxLength(15)]
public string Phone { get; set; }
public ICollection<Apartment> Apartments { get; set; }
public ICollection<Rating> Ratings { get; set; }
}
Apartment
[Table("Apartments")]
public class Apartment
{
[Key]
public int Id { get; set; }
[Required]
[MinLength(24), MaxLength(100)]
public string Title { get; set; }
[Required]
[MinLength(24), MaxLength(250)]
public string Address { get; set; }
[Required]
public int Price { get; set; }
[ForeignKey("User")]
public int UserId { get; set; }
public User User {get; set;}
public ICollection<Rating> Ratings { get; set; }
public ICollection<AptCateg> AptsCategs { get; set; }
}
Ratings
[Table("Ratings")]
public class Rating
{
[Key]
public int Id { get; set; }
public int Value { get; set; }
[ForeignKey("Apartment")]
public int ApartmentId { get; set; }
public Apartment Apartment { get; set; }
[ForeignKey("User")]
public int UserId { get; set; }
public User User { get; set; }
}
I use the commands dotnet ef migrations add InitialDatabase but when I try to use dotnet ef database update it throws the following error in cmd, as in the title
'FK_Ratings_Users_UserId' on table 'Ratings' may cause cycles or
multiple cascade paths
I tried adding as in the EFCore tutorial from here the modelBuilder's Cascade behavior but it doesn't work because I am getting the same error. I have also tried doing the answer from here but the implementation for HasRequired isn't working even if try to install EntityFrameworkCore.Tools.
I understand that there is an issue with a circular thingy going on. From my intuition the program doesn't know what to do in the case of deleting a user, if to drop or not its ratings and apartments or some of that sort, and this is why its acting this way but I can't fix the problem.
My question is, how can I solve this issue as I cannot create my database, and thus I cannot continue working on the project.
Thanks!
You'll have to make the user relationship optional on one of the tables like:
public int? UserId { get; set; }
Making the property type nullable tells EF that a cascade delete is not required here.
You are causing a cyclic reference by adding the User and Apartment to the Ratings entity. User and Apartment entities already have a one-to-many relationship to the Ratings collection.
'FK_Ratings_Users_UserId' on table 'Ratings' may cause cycles or
multiple cascade paths
This is how the Ratings entity should look like:
[Table("Ratings")]
public class Rating
{
[Key]
public int Id { get; set; }
public int Value { get; set; }
}
I have a requirement that I am not sure how to accomplish, in my existing data I have a list of customers, each customer should be assigned a staffMember to work with them, so would this be a 1 to 1 relationship or a 1 to many relationship, having trouble wrapping my head around how to model the data, as I want to figure out how to model this correctly. Since a staff member can be assigned to many different customers How should I model this? Does this look correct?
What I would like is to have the form pull the list of staff members available from the staff table, when inputting a new customer, ideally by the name
which I figure I could probably do using linq..
public class Customer
{
public int CustomerId { get; set; }
public string Name { get; set; }
public string BusinessName { get; set; }
public string Phone { get; set; }
public string Email { get; set; }
public DateTime RequestDate { get; set; }
public Staff Staff { get; set; }
public List<CustomerJob> CustomerJobs { get; set; }
}
public class Staff
{
public int ID { get; set; }
public string Name { get; set; }
public string Phone { get; set; }
public string EMail { get; set; }
public int CustomerId { get; set; }
}
Customer have exactly 1 Staff while a single Staff maybe assigned to more than 1 Customer. So this is a one-to-many relation.
It is better that Customer be aware of its Staff. It could be called AssignedStaff. Staff itslef does not need to have a property to show all its Csutomers. Tough you can extract Customer list of a Staff using a simple query.
My recommended class structure is as follow:
public class Customer
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public string BusinessName { get; set; }
public string Phone { get; set; }
public string Email { get; set; }
public DateTime RequestDate { get; set; }
public Staff AssignedStaff { get; set; }
public List<CustomerJob> CustomerJobs { get; set; }
}
public class Staff
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public string Phone { get; set; }
public string EMail { get; set; }
}
A query for extracting Customer list of a Staff:
var customers = _dbContext.Customers.Where(x => x.AssignedStaff.Id == staffId);
With ASP.NET MVC Core and Entity Framework Core I'm trying to create a simple website.
I've defined my Model:
public class Club
{
[Key]
public int Id { get; set; }
public string Name { get; set; }
public virtual IEnumerable<Team> Teams { get; set; }
}
public class Team
{
[Key]
public int Id { get; set; }
public int ClubId { get; set; }
[MaxLength(32)]
public string Name { get; set; }
public virtual Club Club { get; set; }
}
As well as the corresponding View Models:
public class ClubViewModel
{
public int Id { get; set; }
public string Name { get; set; }
public virtual IEnumerable<TeamViewModel> Teams { get; set; }
}
public class TeamViewModel
{
public int Id { get; set; }
public int ClubId { get; set; }
public string Name { get; set; }
public virtual ClubViewModel Club { get; set; }
}
I've defined an Automapper Profile with the corresponding mappers:
CreateMap<Club, ClubViewModel>();
CreateMap<ClubViewModel, Club>();
CreateMap<Team, TeamViewModel>();
CreateMap<TeamViewModel, Team>();
I try to load a Club entity, with the navigation property Teams included (_context.Club.Include(c => c.Teams).ToList()). This works as expected, it returns a Club with a list of Teams. But when I try to map this instance to a ClubViewModel, I get an 502.3 error and my debug session is ended immediately.
It seems like I am missing something trivial, but I simply do not see it. There's no information in the Windows Event Log and I can't find any usefull information in the IIS Express logging (%userprofile%\documents\IISExpress)
What is causing the crash?
You can't perform this mapping because it is circular. You'll have to remove this line
public virtual ClubViewModel Club { get; set; }
from your TeamViewModel and the mapping should work as expected.