Can ApplicationDbContext.DbSet<Class> be changed on another page and how can I save it separately?

Question

Can ApplicationDbContext.DbSet<Class> be changed on another page and how can I save it separately?

Volk Volk 551

Hi!

I. Let's say I have a controller that has a method that gets some model from the database.

METHOD A

var products = await _db.Products.Where(c =>).ToListAsync();
Product p = products[0];

It has a text description in p.description.

In this method, I make it empty and send it in a model to the view.

p.description = "";

ATTENTION! I'm not doing here:

_db here.SaveChangesAsync();

The page opens - everything is fine!

Model m = new Model();

m.product = p;

return View(m);

But, then the client goes to a page in the browser where METHOD B is called, which does so without var products = await _db.Products:

METHOD B

_db.SaveChangesAsync();

Question: will p.description = "" be saved as an empty string, or will what was originally there?

**

II.** Is it possible to save ApplicationDbContext not all for all, but separately for some table?

n ot this way:** _db.SaveChangesAsync();

like this: _db.Table123_SaveChangesAsync();

Thanks!

AgaveJoe 30,411 Reputation points

2023-12-22T15:01:34.68+00:00
Your question is confusing. My best guess the browser does an HTTP request to Method A and a View is returned. Next, the browser make an HTTP request to Method B.

Question: will p.description = "" be saved as an empty string, or will what was originally there?

The variable p is was disposed when Method A returned the View. You did not share the View so we have no idea what, if anything, is submitted to Method B.

II.** Is it possible to save ApplicationDbContext not all for all, but separately for some table?

Is the problem you are trying to save a disconnected entity passed from the View returned by Method A?

Disconnected entities

public static void Update(DbContext context, object entity) { context.Update(entity); context.SaveChanges(); }

Is there anyway you can you provide a working example so we can see what you are doing?
Volk Volk 551 Reputation points

2023-12-22T16:18:26.46+00:00

In simple words...

I have a private party in the Product - this is the p.description.

It stored something that I don't want to transfer to the View if a person doesn't have access to this information.

Therefore, in method A, I get Product p = products[0]; and erase p.description ="" from it;

But people often have different tabs of the site open and somewhere he can do something and call method B, where something will happen and _db will be called.SaveChangesAsync().

Since p.description = "" happened in method A before, will p be overwritten with an empty description?

How does it happen inside?

Of course, I can send description = "" separately to the View, but everything is tied to classes (objects), as in a good OOP - so first I wonder if there might be an error in such situations.
AgaveJoe 30,411 Reputation points

2023-12-22T17:32:17.5833333+00:00

It stored something that I don't want to transfer to the View if a person doesn't have access to this information.

Why is a user authorized to fetch data they are not allowed to see?

Therefore, in method A, I get Product p = products[0]; and erase p.description ="" from it; But people often have different tabs of the site open and somewhere he can do something and call method B, where something will happen and _db will be called.SaveChangesAsync(). Since p.description = "" happened in method A before, will p be overwritten with an empty description?

It is possible, but you would have had to purposely design a static variable or use a singleton pattern. Basically, create a design where the data can bleed to into different HTTP requests. By default, the DbContext is scoped to a request so each entity is disposed by the time the user sees the View in their browser.

This is something you can test on your own with the Visual Studio debugger.

Of course, I can send description = "" separately to the View, but everything is tied to classes (objects), as in a good OOP - so first I wonder if there might be an error in such situations.

No design should return sensitive data to the client.

It is not clear what OOP has to do with this situation.

Answer accepted by question author

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AgaveJoe 30,411 Reputation points

2023-12-22T15:01:34.68+00:00

Your question is confusing. My best guess the browser does an HTTP request to Method A and a View is returned. Next, the browser make an HTTP request to Method B.

Question: will p.description = "" be saved as an empty string, or will what was originally there?

The variable p is was disposed when Method A returned the View. You did not share the View so we have no idea what, if anything, is submitted to Method B.

II.** Is it possible to save ApplicationDbContext not all for all, but separately for some table?

Is the problem you are trying to save a disconnected entity passed from the View returned by Method A?

Disconnected entities

public static void Update(DbContext context, object entity) { context.Update(entity); context.SaveChanges(); }

Is there anyway you can you provide a working example so we can see what you are doing?
Volk Volk 551 Reputation points

2023-12-22T16:18:26.46+00:00

In simple words...

I have a private party in the Product - this is the p.description.

It stored something that I don't want to transfer to the View if a person doesn't have access to this information.

Therefore, in method A, I get Product p = products[0]; and erase p.description ="" from it;

But people often have different tabs of the site open and somewhere he can do something and call method B, where something will happen and _db will be called.SaveChangesAsync().

Since p.description = "" happened in method A before, will p be overwritten with an empty description?

How does it happen inside?

Of course, I can send description = "" separately to the View, but everything is tied to classes (objects), as in a good OOP - so first I wonder if there might be an error in such situations.
AgaveJoe 30,411 Reputation points

2023-12-22T17:32:17.5833333+00:00

It stored something that I don't want to transfer to the View if a person doesn't have access to this information.

Why is a user authorized to fetch data they are not allowed to see?

Therefore, in method A, I get Product p = products[0]; and erase p.description ="" from it; But people often have different tabs of the site open and somewhere he can do something and call method B, where something will happen and _db will be called.SaveChangesAsync(). Since p.description = "" happened in method A before, will p be overwritten with an empty description?

It is possible, but you would have had to purposely design a static variable or use a singleton pattern. Basically, create a design where the data can bleed to into different HTTP requests. By default, the DbContext is scoped to a request so each entity is disposed by the time the user sees the View in their browser.

This is something you can test on your own with the Visual Studio debugger.

Of course, I can send description = "" separately to the View, but everything is tied to classes (objects), as in a good OOP - so first I wonder if there might be an error in such situations.

No design should return sensitive data to the client.

It is not clear what OOP has to do with this situation.

Answer 1

Ah, the intricacies of Entity Framework. If I understood correctly, you ave a model XX with property Description. Model XX is available to many users, but only some users should be able to access XX.Description, so you blank it out in MethodA for people without access. MethodA is not shown in the question, but from context I am concluding that MethodA returns a view capable of editing the object. When the view posts, it posts to MethodB, in charge of saving updates. You want to make sure the XX.Description remains intact if the user was an underprivileged user.

If my understanding is correct, the simplest way would be to have a MethodBPrivileged and a regular MethodB, where the former will update XX.Description, but the latter won't.

In Entity Framework jargon... I'm unsure as I avoid it like the plague. Can EF map 2 models to the same table? If it can, create 2 models: One that contains the Description property, and one that doesn't. Then, in the server's MethodA routine, by virtue of checking the logged-in privileges, determine which model to use and which view to send: A view that posts to MethodB, or a view that posts to MethodBPrivileged.

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Can ApplicationDbContext.DbSet<Class> be changed on another page and how can I save it separately?

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