C#•14mo ago

I require some help understanding MVC and Database loading/updating

Hi, I'm very new to MVC and new to ASP.NET CORE, So these questions may be all over the place. I do have an understanding of C# & Object-Oriented programming.

I'm trying to make a web application that has two tables, a

Users

Users

table and a

UserPhoneNumbers

UserPhoneNumbers

table, for this app I am allowing a single

User

User

to have Multiple

UserPhoneNumber

UserPhoneNumber

attached to it. I understand that I'll need a Model for each.

Here are my two example models

c#
public class User
{
    [Key, Required]
    public string AccountId { get; set; }

    [StringLength(255), Required]
    public string Email { get; set; }
    
    [StringLength(255), Required]
    public string FirstName { get; set; }
    
    [StringLength(255), Required]
    public string LastName { get; set; }
    
    public ICollection<UserPhoneNumber> UserPhoneNumbers { get; set; }
}

public class UserPhoneNumber
{
    [Key, StringLength(32), Required]
    public string? UserPhoneNumberId { get; set; }
    
    [StringLength(32), Required]
    public string? PhoneNumber { get; set; }
    
    public User User { get; set; }

}

c#
public class User
{
    [Key, Required]
    public string AccountId { get; set; }

    [StringLength(255), Required]
    public string Email { get; set; }
    
    [StringLength(255), Required]
    public string FirstName { get; set; }
    
    [StringLength(255), Required]
    public string LastName { get; set; }
    
    public ICollection<UserPhoneNumber> UserPhoneNumbers { get; set; }
}

public class UserPhoneNumber
{
    [Key, StringLength(32), Required]
    public string? UserPhoneNumberId { get; set; }
    
    [StringLength(32), Required]
    public string? PhoneNumber { get; set; }
    
    public User User { get; set; }

}

Lets presume I have a working database and can perform basic CRUD operations.
Here are my questions:

JasonOP•10/27/24, 5:11 PM

How do models work?
I have these two models, I add the migrations & update the database. It creates these two tables

Users

Users

and

UserPhoneNumbers

UserPhoneNumbers

what next? How do I add or load the data that is already in the table? Lets for a moment say I have the following user:

My presumption was to create a method inside of the class and inside that method check to see if the database already contains an entry matching or . However upon trying to research the topic I got lost down a rabbit hole and found multiple different articles that say I shouldn't have anything other then the properties that relate to the table inside the Models class & that I should create either a "Service" or "Repository" class that handles the CRUD operations. I'm just looking for confirmation on that being correct. I guess what I'm asking is:

Should the class ONLY contain the properties corresponding to the table?
Should I be using a Repository/Service class for my CRUD operations?*
Whats the difference between Repository class and a Service class?

How on earth do database relationships work?
In the two example classes I provided above, In

User

User

I have a and in

UserPhoneNumber

UserPhoneNumber

Lets say I already have a user loaded from the database How would i get the phone number, would it be as simple as ?

I know that last question was a bit vague, but my understanding of database relationships is very little.

JJason **How do models work?** I have these two models, I add the migrations & update t...

Angius•10/27/24, 5:12 PM

You use the
```
DbContext
```
```
DbContext
```
you also must've made

Angius•10/27/24, 5:13 PM

With LINQ, since that's how EF does it

Angius•10/27/24, 5:16 PM

Find:

Create:

Update:

Delete:

Angius•10/27/24, 5:16 PM

Getting the related data can be done two ways

Angius•10/27/24, 5:19 PM

By including everything from that relationship
By selecting only what you need into a DTO
```cs
sealed record UserWithNumbers(int Id, string Name, string[] PhoneNumbers);

var user = await context.Users
.Where(u => u.Id == id)
.Select(u => new UserWithNumbers(
u.Id,
$"{u.FirstName} {u.LastName}",
u.PhoneNumbers.Select(pn => pn.Number)
))
.FirstOrDefaultAsync();
```

Angius•10/27/24, 5:19 PM

The latter is the recommended way

Angius•10/27/24, 5:19 PM

In general, database models should never leave the application boundary. All incoming and outgoing requests should be their own models, DTOs

Angius•10/27/24, 5:20 PM

DTO — Data Transfer Object

Angius•10/27/24, 5:20 PM

Sometimes also called POCOs, Plain Old C# Objects

JasonOP•10/27/24, 5:25 PM

Okay, Thanks for that info, however I'm still stuck on these three little sub questions:

Should the Models.User class ONLY contain the properties corresponding to the table?
Should I be using a Repository/Service class for my CRUD operations?
Whats the difference between Repository class and a Service class?

Angius•10/27/24, 5:28 PM

Yes
Some people believe so, some people don't. One thing for sure, you should not be using a generic repository if you decide to use them, but rather specific repositories for each model
The difference is kinda blurry, but in general repositories contain mostly very generic code (, , , etc) while services are a bit more specific (, , , etc)

JasonOP•10/27/24, 5:34 PM

Lets see if i got this, its a little generic, but would this be a correct file structure

Where are litterally just the tables of the database,
Where are generic classes,
Where contains a interface that would layout the basic CRUD requirements for my Repository classes
Where would implement the specific methods required for each model, i.e the CRUD methods described in the

Angius•10/27/24, 5:35 PM

This would be a very classic, enterprise-like architecture, yes

JasonOP•10/27/24, 5:37 PM

Early in my testing I created a class, Given what you have told me, I'm on the correct idea, but my implementation of the and methods are wrong

https://gist.github.com/Nashy1232/e12d68e5d21ed73ffc9b7556efef13c5

Gist

0fYSC1UMBA.txt

GitHub Gist: instantly share code, notes, and snippets.

Angius•10/27/24, 5:40 PM

Yeah, that seems extremely overcomplicated

Angius•10/27/24, 5:41 PM

I'm stunned that you wrote all of that before googling "ef how check if exist" lmao

JasonOP•10/27/24, 5:42 PM

I wrote that very much with the help of google, but for the love of me I can't remember what I googled. I just remember my goal was to make the most generic / reusable method to get an entry from a database

Angius•10/27/24, 5:43 PM

EF already provides the most generic/reusable methods

JasonOP•10/27/24, 5:48 PM

So, i could compact that entire class down into just this?
https://gist.github.com/Nashy1232/fc8cec276582df95c3278449a697c007

Gist

rhJippuoi2.txt

GitHub Gist: instantly share code, notes, and snippets.

JasonOP•10/27/24, 5:49 PM

by adding replacing with:

Angius•10/27/24, 5:50 PM

Or just don't have the method at all, and simply use

Angius•10/27/24, 5:51 PM

Your also seems like a ghetto version of a GUID

JasonOP•10/27/24, 5:51 PM

GUID?

Angius•10/27/24, 5:51 PM

Globally Unique IDentifier

MODiX•10/27/24, 5:51 PM

Angius

REPL Result: Success

Result: Guid

Compile: 312.750ms | Execution: 22.066ms | React with ❌ to remove this embed.

JasonOP•10/27/24, 5:53 PM

huh, I guess technically it is, I wanted an ID that was 4 sections of 4 characters serperated by a hash, for example

Angius•10/27/24, 5:53 PM

Why?

JasonOP•10/27/24, 5:54 PM

Good question...

Angius•10/27/24, 5:54 PM

IMO you could even just use sequential IDs

JasonOP•10/27/24, 5:55 PM

I guess originally I didn't want them just auto increment index

JasonOP•10/27/24, 5:55 PM

eventually I planend on having an API where you can provide account ID & a token

JasonOP•10/27/24, 5:55 PM

but honestly, i'd be better of creating an API key and token that can be revoked

JasonOP•10/27/24, 5:56 PM

and generate the API key independent of the account ID

Angius•10/27/24, 5:56 PM

That would be ideal, yeah

Angius•10/27/24, 5:56 PM

Well, OAuth2 would be ideal, but that's it's own can of worms

JasonOP•10/27/24, 5:57 PM

At the moment, my goal is to familiarise myself with the MVC style and the basics before even attempting to deal with authentication and the likes

JasonOP•10/27/24, 5:58 PM

I think I'm going to keep the GenerateUniqueIdentifier method, but I think it needs to be reworked as I do want each account to have a unique account id that isn't auto-incremented

Angius•10/27/24, 5:59 PM

Or just let the database generate a GUID

Angius•10/27/24, 5:59 PM

But sure, whatever works for you

AAngius Or just let the database generate a GUID

JasonOP•10/27/24, 5:59 PM

huh, how?

Angius•10/27/24, 6:02 PM

on the PK should work

JasonOP•10/27/24, 6:02 PM

right?

JasonOP•10/27/24, 6:02 PM

i like your way better

Angius•10/27/24, 6:02 PM

Or what you sent, yes

Angius•10/27/24, 6:03 PM

Assuming the database you're using supports GUID/UUIDs

JasonOP•10/27/24, 6:03 PM

mariaDB, I'd have to double check that

JasonOP•10/27/24, 6:15 PM

It doens't look like it does support it

Angius•10/27/24, 6:16 PM

You could always just set the key in the constructor and make the setter private

JasonOP•10/27/24, 6:16 PM

but it looks like i can override the method to have it work in the same way