I'm trying to learn how to use the ASP.NET MVC 4 and Entity FrameWork 5, and I'm a bit confused by scaffolding for Drop Down Lists.
I have three classes:
public class ScopeType
{
public int ScopeTypeId { get; set; }
[Required]
public string Type { get; set; }
}
public class ScopeManufacturer
{
public int ScopeManufacturerId { get; set; }
[Required]
[Display(Name="Manufacturer Name")]
public string Name { get; set; }
}
public class Scope
{
public int ScopeId { get; set; }
[Required]
public ScopeManufacturer ScopeManufacturer { get; set; }
[Required]
public string Name { get; set; }
[Required]
public ScopeType ScopeType { get; set; }
[Required]
public int Aperture { get; set; }
[Required]
public int FocalLength { get; set; }
}
Essentially, the first two classes are just lists of values that I want to appear in the drop downs on the 'Scope' create/edit forms. It's a 1 to 1 relationship.
I build the solution, and then add scaffolded controllers and views. Unfortunately, for the 'Scope' controller and views, the ScopeType and ScopeManufacturer navigation properties are ignored; no drop down lists are generated.
I then found on Google examples where people describe specifying the relationship between items by creating properties of integers, with the same name as the Id on the related thing. Therefore, I deleted the controllers and views, and tried again with:
public class Scope
{
public int ScopeId { get; set; }
[Required]
public int ScopeManufacturerId { get; set; }
[Required]
public string Name { get; set; }
[Required]
public int ScopeTypeId { get; set; }
[Required]
public int Aperture { get; set; }
[Required]
public int FocalLength { get; set; }
}
This still didn't scaffold drop down lists for me - rather, it gave me 2 extra fields for me to type integers into.
What am I doing wrong, or am I mistaken in believing that the scaffolding in MVC 4 will generate drop down lists for 1 to 1 relationships like 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 am working on ASP.NET Core application which uses Entity framework core. I am using code first approach to create database model. I am trying the get one-to-many relationship (one user can have multiple products) between following two classes but in database diagram, I can not see that relationship.
public class SystemUser : IdentityUser
{
public SystemUser()
{
this.ProductToUser = new HashSet<ProductsToUser>();
}
[StringLength(200)]
[Required]
public string FullName { get; set; }
[Required]
[StringLength(200)]
public string Address { get; set; }
[Required]
public int PinNo { get; set; }
[Required]
public int StateId { get; set; }
[Required]
public int CountryId { get; set; }
[Required]
public DateTime RegisterDate { get; set; }
public virtual ICollection<ProductsToUser> ProductToUser { get; set; }
}
public class ProductsToUser
{
[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public int Id { get; set; }
[Required]
public string UserId { get; set; }
[Required]
public int ProductID { get; set; }
[ForeignKey("UserId")]
public SystemUser SystemUser { get; set; }
}
Below is the screenshot of database diagram.
As you can see in diagram it is not showing relationship. But I am getting foreign key constraint in ProductsToUser table as shown below
How do I resolve this issue?
I have two classes in my model
[Table("tblPackages")]
public class Packages
{
public int Id { get; set; }
[Required]
[Display(Name = "Package Type")]
public int TypeId { get; set; }
[Display(Name = "No of SMS")]
public int AllowedSMS { get; set; }
[Display(Name = "Time Span in Days")]
public int? TimeSpan { get; set; }
public decimal Price { get; set; }
}
[Table("tblPackageTypes")]
public class PackageTypes
{
public int Id { get; set; }
public string Name { get; set; }
public string Details { get; set; }
public DateTime DueDate { get; set; }
}
and the table is same. now i need to get all from class Packages and just Name from class PackageTypes. How can i do by just using Entity Framework
Add a PackageTypes navigation property to your Packages class and access it by name:
[Table("tblPackages")]
public class Packages
{
public int Id { get; set; }
[Required]
[Display(Name = "Package Type")]
public int PackageTypesId { get; set; }
public PackageTypes PackageTypes { get; get; }
[Display(Name = "No of SMS")]
public int AllowedSMS { get; set; }
[Display(Name = "Time Span in Days")]
public int? TimeSpan { get; set; }
public decimal Price { get; set; }
}
By convention, Entity Framework will match the PackageTypesId and PackageTypes properties based on the naming (although you can use different names if you configure it to do so, but that's a more advanced topic).
Now you can access the Name directly from your Packages objects:
myPackage.PackageTypes.Name
Also, you might want to think about your classes in the singular, not the plural. The class represents a single Package, not the entire collection. Same with the PackageType. It makes your code more understandable:
Package myPackage = new Package();
myPackage.PackageType.Name
Only use plural if your class truly represents the entire collection and not a single item.
Use a navigation property, you will need a FK relationship between Packages and PackageTypes:
[Table("tblPackages")]
public class Packages
{
public int Id { get; set; }
[Required]
[Display(Name = "Package Type")]
public int TypeId { get; set; }
[Display(Name = "No of SMS")]
public int AllowedSMS { get; set; }
[Display(Name = "Time Span in Days")]
public int? TimeSpan { get; set; }
public decimal Price { get; set; }
public int PackageTypesId {get;set;}
public virtual PackageTypes {get;set;}
}
[Table("tblPackageTypes")]
public class PackageTypes
{
public int Id { get; set; }
public string Name { get; set; }
public string Details { get; set; }
public DateTime DueDate { get; set; }
public ICollection<Packages> {get;set;}
}
Like the previous answer states you need a navigation property. From your code I assume TypeId is FK to Id in PackageTypes. If this is so, simply create a property named Type of the type PackageType. When EF finds a navigation property to another entity it tries to find the property with the FK by appending the suffix Id or _Id.
If you on the other want a true composite object joining in fields from several tables you should use a view for this!
Regards
Håkan