Giving the sample below, is there any way to have Address in the same table as User without making use of table splitting or owned types (eg like EF6 complex types)? The generated SQL prevents me from using it and complex types does not seem to be supported in EF Core 3:
public class User
{
public int Id { get; set; }
public Address Address { get; set; }
public string UserName { get; set; }
}
public class Address
{
public string StreetAddress { get; set; }
public string City { get; set; }
public string State { get; set; }
public string ZipCode { get; set; }
}
The only other options I see would be to map Address to its own table.
I will use a 1 to 0..1 relationship or include the properties in User directly.
Nevertheless, using Owned Types as a replacement for ComplexTypes like in EF 6 is horrible , if not completely useless from a SQL perspective, and I cannot see any reason for the joins. Maybe someone can clarify a proper justification for completness
Related
Background:
Given the following two entities joint through one to one relationship:
public partial class Parent
{
public long Id { get; set; }
public string Email { get; set; }
public virtual Details Details{ get; set; }
}
public partial class Details
{
public long Id { get; set; }
public long ParentId{ get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime Dob { get; set; }
public virtual Parent Parent { get; set;}
}
And having the following Query model:
public class Query
{
public string Email { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime? Dob { get; set; }
}
Question
How can I apply the Query as IQueryable on the Parent (or Details) entity?
Notes based on the use case I have:
Query class can't have two sub-classes for Parent and Details (it should be flattened)
DB SQL query should fetch results that matches both conditions in Parent and Details (if condition fail for details, then parent shouldn't be in the results).
There might be long list of optional fields in Query model. It means that the DB query should be dynamic and smart enough to know how to build the query and to know each field in Query belongs to which entity Parent or Details (i.e. I don't want a solution where I add conditions to check whether Dob exist in the Query or not)
Use case:
I'm using HotChocolate framework to integrate GraphQL which uses expression trees to build the queries. The issue I'm trying to solve is mentioned here
Your support and suggestions would be highly appreciated!
I managed to handle this issue by creating a View on the DB which joins both tables to act as single entity where I can filter, paginate and sort regardless whether it is one to one linked tables or it is single table.
Then did reverse engineering of that view using this link to be integrated with EntityFramework and finally managed to handle IQueryable on both entities.
In case of any other option available and suitable for HotChocolate, please add another answer to enhance my existing solution.
How should I design entity classes for tables? Classes map their relationships? How should I modify it? I don't want to use code first or DB first, just write code manually to add relationships.
public partial class Ip
{
public int Id { get; set; }
public string Ip1 { get; set; }
public int UserId { get; set; }
}
public partial class U
{
public int Id { get; set; }
public string UserName { get; set; }
public string Pwd { get; set; }
}
Expect of Code First and Database First we have Model First in entity framework.
First idea you can add relation between tables on database (server side handling).
Second idea you can write sql query code then execute in SeedData Method. but you need to check relation not exist that table.
What is the difference between foreign key reference using Id vs object.
For example:
FK relation using Id
class Product
{
public int Id { get; set; }
public string Name { get; set; }
public string PhoneNumber { get; set; }
public int CategoryId { get; set; }
}
vs
FK relation using object
class Product
{
public int Id { get; set; }
public string Name { get; set; }
public string PhoneNumber { get; set; }
public Category Category { get; set; }
}
I have noticed from database that by using Id property the column essentially becomes non-null field.
Is that the only difference?
I think we can't query multiple tables at once i.e.querying related data?
When should I choose to use either options?
In your first example you're not adding a relationship, just an integer property named CategoryId.
In your second example, Entity Framework will create an integer column named "Category_ID", but you will be not be able to see this property in your model, so I like to explicitly add it my self and be able to use it along with the navigation property.
class Product
{
public int Id { get; set; }
public string Name { get; set; }
public string PhoneNumber { get; set; }
[ForeignKey("Category")]
public int CategoryId { get; set; }
public Category Category{get;set;}
}
This way you can also control the data type of CategoryId, so you could make it optional (nullable)
public int? CategoryId { get; set; }
*The foreign key data annotation is not needed, unless you have property or navigation property names that do not follow the naming convention for foreign key property names (Bardr), it doesn't harm to explicitly declare it either for clarity purposes
This implies that you're creating a 1 to many relationship (1-*) with products and categories, so in your Category class you would be adding a collection navigation property for products
class Category
{
public int Id{ get; set;}
public string Name{ get; set; }
...
public ICollection<Product> Products{get; set;}
}
Basically it depends on your use case and what type of loading related data you choose. Whether you use Id or object reference or full relationship on both sides (Id and object) it depends on your overall application architecture. If you wil go and use full or object reference everywhere, you will (probably) end up with a mess, and you won't know whether you should query for some entities using their repository or if it'll be okay to include them to some other query. I highly recommend you to take a look at this book, especially chapter 19 (Aggregates) and 21 (Repositories). There you have an in-depth explanation of what I meant and much more. (This does not only apply to applications built in DDD way)
I'm working on mapping a legacy application with classes and use EntityFramework against it.
One flaw I have found in this legacy database is that multiple tables refer to a specific table through 2 different fields.
I'm not sure if this is possible and why I can't seem to find anything about it so I am here.
Here is a visual sample:
public class Term {
[Key]
public string Id { get; set; } // sample value: "12-34-56/78"
public string CleanId { get; set; } // sample value: "12345678" (basically the Id without special characters)
public DateTime Date { get; set; }
}
public class App {
public int Id { get; set; }
public string CleanTermId { get; set; } // foreign key is in Term class using the `CleanId` field
}
public class Question {
public int Id { get; set; }
public string TermId { get; set; } // foreign key is in Term class using the `Id` field
}
How can I properly add a navigational property from App and Question to the Term class using either DataAnnotations (preferred) to Fluent API? I do not require a navigational property from Term to App or Question but it's ok if your answer includes it.
Let me know if this is not clear.
Joining on fields other than Primary Key was something that isnt supported in EF versions prior to EF Core, however with your mention of it being a legacy app I doubt you would want to overhaul it to be able to use EF Core.
There was a User Voice request for the feature to be added Here which the response is that they had no plans to add this functionality into EF6 - so Core would be the only way to really do this.
In terms of your classes you would be able to link Question and Term as its based PK - FK, but the App to Term is basing both on non-PK fields, even with a Unique constraint on the DB, this is something not supported in EF prior to Core
Hi this is the correct Code:
public class Term
{
[Key]
public string Id { get; set; }
public string CleanId { get; set; }
public DateTime Date { get; set; }
}
public class App
{
public int Id { get; set; }
[ForeignKey("CleanTermId")]
public Term MyTerm { get; set; }
public string CleanTermId { get; set; }
}
public class Question
{
public int Id { get; set; }
[ForeignKey("TermId")]
public Term MyTerm { get; set; }
public string TermId { get; set; }
}
I have started to learn ASP.NET MVC, and at this time of studying I wanna create simple blog site. I have decided to use ASP.NET MVC and ORM Entity Framework. Probably you have some useful links about this theme?
I tried to start from creating Model code first.
i have 3 classes Post, User(User can be admin), Comments.
Please I need help to make the relations between the database models. I have code like this right now:
public class Post
{
public int PostId { get; set; }
public string Title { get; set; }
public string Content { get; set; }
public List<Comment> Comments { get; set; }
public DateTime PublishDate { get; set; }
}
public class User
{
public readonly bool IsAdmin { get; set; }
public string FirstName { get; set; }
public string SecondName { get; set; }
public string Email { get; set; }
public string Password { get; set; }
public DateTime DateOfBirthday { get; set; }
public string Country { get; set; }
public string City { get; set; }
public List<Post> Posts { get; set; }
public List<Comment> Comments { get; set; }
}
public class Comment
{
public int CommentId { get; set; }
public string UserName { get; set; }
public string Content { get; set; }
public DateTime PublishDate { get; set; }
}
These are my classes to create database tables, but I'm not sure how make relations like many-to-one.
Is it correct to make List of Comments for Post or just write int CommentID?? I have never use database very deep, just saw a few lessons. Can somebody to advise how make repository or correct my Model code?
Thank you very much!
There are plenty of good tutorials out there about how to do this. This one, for example:
http://www.asp.net/mvc/tutorials/getting-started-with-ef-using-mvc/creating-an-entity-framework-data-model-for-an-asp-net-mvc-application
To answer some of your questions, yes, the name CommentId is correct; every EF class that you want stored in the database must have either a field called Id or a field called MyClassId (where "MyClass" is the name of your class). I've found that the latter makes your life easier, especially when doing joins.
Unless you have some relationships that EF can't figure out automatically, you don't have to specify the relationships yourself: EF will automatically detect the correct relationship for you. I don't see anything in your code that EF can't handle automatically.
One thing you will have to do is make the List<Post> and List<Comment> fields virtual; that way EF can supply database-backed relationships.
Good luck.
I enjoyed the Building an MVC 3 App with Code First and Entity Framework 4.1
tutorial. Includes a video that I found very easy to follow.