C#•17mo ago

❔ Problem while adding same article with different quantity on 2 different tables

I'm using EF Core and WPF. Once I add same article with different quantity on 2 different tables,quantity is replaced on all tables.

58 Replies

Angius•17mo ago

Make sure it's not actually the same item, as in, the same reference The change tracker does keep track of it

XANDROOP•17mo ago

so what would be the best way to solve it Should I disable change tracker?

Angius•17mo ago

First, what's the relationship supposed to be?

XANDROOP•17mo ago

many to many

Angius•17mo ago

Many to many between article and table?

XANDROOP•17mo ago

articles can be on multiple tables and tables can have multiple articles

Angius•17mo ago

And, I assume, the quantity is the quantity of a given article in a given table?

XANDROOP•17mo ago

That's right

Angius•17mo ago

For example, Table1 can have 10 apples, and Table2 24 apples?

XANDROOP•17mo ago

Right

Angius•17mo ago

Well, in that case, place the quantity not on the article, but on the join table

XANDROOP•17mo ago

Im not sure if I get you

Angius•17mo ago

Many-to-many requires a join table

XANDROOP•17mo ago

Ohh wait

Angius•17mo ago

EF can hide it, but it does exist And you can tap into it

XANDROOP•17mo ago

I understand

XANDROOP•17mo ago

Angius•17mo ago

Or you can set it up explicitly Yep

XANDROOP•17mo ago

You mean to add here quantity right?

Angius•17mo ago

Exactly

XANDROOP•17mo ago

I actually thought about that but someone said it's not possible on stackoverflow you can't add custom columns in join table

Angius•17mo ago

Of course you can

XANDROOP•17mo ago

I was really thinking that would be the best solution until I found someone said that and I gived up on that idea.

Angius•17mo ago

public class TableArticles
{
    public Article Article { get; set; }
    public int ArticleId { get; set; }
    public Table Table { get; set; }
    public int TableId { get; set; }
    public int Quantity { get; set; }
}

public class TableArticles
{
    public Article Article { get; set; }
    public int ArticleId { get; set; }
    public Table Table { get; set; }
    public int TableId { get; set; }
    public int Quantity { get; set; }
}

builder.Entity<Table>()
    .HasMany(t => t.Articles)
    .WithMany(a => a.Tables)
    .WithJoinEntity<TableArticles>();

builder.Entity<Table>()
    .HasMany(t => t.Articles)
    .WithMany(a => a.Tables)
    .WithJoinEntity<TableArticles>();

And on your Article you can have a List<Table> and a List<TableArticles> And vice versa

XANDROOP•17mo ago

I will have to create new model called TableArticles?

Angius•17mo ago

Yep Or you can create a DbSet<TableArticles> and just tap into it directly

XANDROOP•17mo ago

Okay pal I will try to do what you said and I really hope it will work 😄 I will fill you in I just need couple of minutes

Angius•17mo ago

I have something like that set up in my project, so I can dig for that code if need be to show you an example I'll be back in an hour or so

XANDROOP•17mo ago

Okay one more thing quantity from Article should be removed right?

Angius•17mo ago

yep

XANDROOP•17mo ago

Okay

XANDROOP•17mo ago

XANDROOP•17mo ago

And If I don't have anymore article.Quantity how else should I call it?

XANDROOP•17mo ago

Can I do it like this? Do I have to create method to save this table or EF will do this for me since this is many to many

mtreit•17mo ago

Trusting stack overflow was your first mistake😛

XANDROOP•17mo ago

Ahahahahahha Where should I learn new stuff then?

mtreit•17mo ago

Stack Overflow has lots of good answers and lots of garbage answers and if you don't have a lot of experience it's hard to know which is which. This Discord is a good resource to leverage, as evidenced by this discussion.

XANDROOP•17mo ago

Thank you After creating new model will i still have articleTable join table? Or it will be replaced with new one

Angius•17mo ago

Yeah, it will still exist in the db Just make sure it's named the same and EF should pick it up

XANDROOP•17mo ago

So wait I will than have join table and one more?

Angius•17mo ago

No You'll only have one table You might need to provide a default value for the Count though, since the data that exists in the database right now doesn't have that After that, in the next migration, you'll be able to just remove the default value though

XANDROOP•17mo ago

How I will access to quantity? I cant do article.quantity anymore right?

Angius•17mo ago

You'll need to know the article and the table first, yes

XANDROOP•17mo ago

And add those values to my new model right? And create crud for that model

Angius•17mo ago

Then you can do

article.TableArticles.Where(ta => ta.TableId == tableId).First().Quantity;

article.TableArticles.Where(ta => ta.TableId == tableId).First().Quantity;

table.TableArticles.Where(ta => ta.ArticleId == articleId).First().Quantity;

table.TableArticles.Where(ta => ta.ArticleId == articleId).First().Quantity;

var quantity = await _context.TableArticles.
    .Where(ta => ta.TableId == tableId && ta.ArticleId == articleId)
    .Select(ta => ta.Quantity)
    .FirstOrDefaultAsync();

var quantity = await _context.TableArticles.
    .Where(ta => ta.TableId == tableId && ta.ArticleId == articleId)
    .Select(ta => ta.Quantity)
    .FirstOrDefaultAsync();

XANDROOP•17mo ago

Okay and I should have crud options right? For that model of course

Angius•17mo ago

If you need them, yes

XANDROOP•17mo ago

One more think This is called junction table right?

Angius•17mo ago

Yep

XANDROOP•17mo ago

Okay thank you so much for all of these informations

Angius•17mo ago

Or a "join table", or a "pivot table" I even seen used once or twice

XANDROOP•17mo ago

All the best for you

Angius•17mo ago

Anytime

XANDROOP•17mo ago

I can't create Crud for ArticleTable because I didn't do DBset Also I can't do article.ArticleTable It doesnt exist And If you do this _context.TableArticles It means you added it to DbSet<>? Right

Angius•17mo ago

Make it exist Yes

XANDROOP•17mo ago

Ok, I made it work with EF Core Is there any way to make it "easier" someone told me I could use dictionary<int,List<Article>> and save tableId in int and all articles from table to that list in dictionary

Angius•17mo ago

Sure, you can select the results into a dictionary

Accord•17mo ago

Was this issue resolved? If so, run /close - otherwise I will mark this as stale and this post will be archived until there is new activity.

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❔ Problem while adding same article with different quantity on 2 different tables