C#•2y ago

❔ Struggling to delete a many to many relation

    public async Task<IStatusCodeActionResult> Remove(long areaId, long houseId)
    {
        var area = await _context.Areas
            .Include(s => s.Houses)
            .FirstOrDefaultAsync(s => s.Id == areaId);
        
        if (area == null)
            return BadRequest("Area does not exist");
        
        var house = await _context.Houses
            .FirstOrDefaultAsync(s => s.Id ==houseId);
        
        if (house == null)
            return BadRequest("House does not exist");

        var success = area.Houses.Remove(house);
        
        if (success == false)
            return BadRequest("House not found in this area");
        
        _context.Areas.Update(area);
        
        await _context.SaveChangesAsync();

    public async Task<IStatusCodeActionResult> Remove(long areaId, long houseId)
    {
        var area = await _context.Areas
            .Include(s => s.Houses)
            .FirstOrDefaultAsync(s => s.Id == areaId);
        
        if (area == null)
            return BadRequest("Area does not exist");
        
        var house = await _context.Houses
            .FirstOrDefaultAsync(s => s.Id ==houseId);
        
        if (house == null)
            return BadRequest("House does not exist");

        var success = area.Houses.Remove(house);
        
        if (success == false)
            return BadRequest("House not found in this area");
        
        _context.Areas.Update(area);
        
        await _context.SaveChangesAsync();

27 Replies

dave1OP•2y ago

been looking at it for a long time now, just need a sanity check if that's how it should be, then i must have fucked up somewhere else i think i'm going to just delete it manually, no idea how to debug this it's supposed to simply remove that sepcific house from the area, it's a many to many

Tvde1•2y ago

when you fetch the Area, you are not including the list of houses. Do that through

await _context.Areas
    .Include(x => x.Houses)
    .FirstOrDefault(...);

await _context.Areas
    .Include(x => x.Houses)
    .FirstOrDefault(...);

You would see that every area you fetch has no houses, if you omit the .Include

dave1OP•2y ago

sorry should have updated it, i have that in my current version now when i step debug through, i see it's removed it , i get no errors, but when i test the db after, that relation still exists

Tvde1•2y ago

_context.Areas.FirstOrDefaultAsync(s => s.Id == areaId);

_context.Areas.FirstOrDefaultAsync(s => s.Id == areaId);

will result into

SELECT TOP 1 *
FROM Areas
WHERE id == @areaId;

SELECT TOP 1 *
FROM Areas
WHERE id == @areaId;

and

_context.Areas
    .Include(x => x.Houses)
    .FirstOrDefaultAsync(s => s.Id == areaId);

_context.Areas
    .Include(x => x.Houses)
    .FirstOrDefaultAsync(s => s.Id == areaId);

will result into

SELECT *
FROM Areas a
WHERE id == @areaId
INNER JOIN Houses h
  ON h.AreaId = a.Id

SELECT *
FROM Areas a
WHERE id == @areaId
INNER JOIN Houses h
  ON h.AreaId = a.Id

dave1OP•2y ago

aye i'm presuming that the change tracker needs some change to track, so removing nothing, it cant track that change

Tvde1•2y ago

you can try

    public async Task<IStatusCodeActionResult> Remove(long areaId, long houseId)
    {
        var area = await _context.Areas
            .Include(s => s.Houses)
            .FirstOrDefaultAsync(s => s.Id == areaId);
        
        if (area == null)
            return BadRequest("Area does not exist");
        
        var house = area.Houses.FirstOrDefault(s => s.Id ==houseId);
        
        if (house == null)
            return BadRequest("House does not exist");

        var success = area.Houses.Remove(house);
        
        if (success == false)
            return BadRequest("House not found in this area");
        
        await _context.SaveChangesAsync();

    public async Task<IStatusCodeActionResult> Remove(long areaId, long houseId)
    {
        var area = await _context.Areas
            .Include(s => s.Houses)
            .FirstOrDefaultAsync(s => s.Id == areaId);
        
        if (area == null)
            return BadRequest("Area does not exist");
        
        var house = area.Houses.FirstOrDefault(s => s.Id ==houseId);
        
        if (house == null)
            return BadRequest("House does not exist");

        var success = area.Houses.Remove(house);
        
        if (success == false)
            return BadRequest("House not found in this area");
        
        await _context.SaveChangesAsync();

it makes one less db call and the update is not necessary, savechanges will save everything you change to entities

dave1OP•2y ago

oh you know, i have actually tried tha aswell hahaha i wasnt sure if it was required cheers, so ef context is doing more magic under the hood than i presumed, good to know

Tvde1•2y ago

yes, any entity you get from it will have its changes tracked (unless you explicitly tell it not to)

        var area = await _context.Areas
            .AsNoTracking()
            .Include(s => s.Houses)
            .FirstOrDefaultAsync(s => s.Id == areaId);

        var area = await _context.Areas
            .AsNoTracking()
            .Include(s => s.Houses)
            .FirstOrDefaultAsync(s => s.Id == areaId);

would make EF not track changes

dave1OP•2y ago

ah i had assumed it was on the action of Update/Create etc. it was tracking from that point

Tvde1•2y ago

honestly I'm not sure why your original code didn't work. It feels as if it should also work

dave1OP•2y ago

yeah you see i'm at that point aswell, i think i've fkd up the entities at least i know that side is fine cheers Tvde1, appreciated

Tvde1•2y ago

you think you messed up the entities?

dave1OP•2y ago

maybe, that's the only other moving part, or maybe my test is wrong oh god, i think it's the test

Tvde1•2y ago

😁 happens to the best of us

dave1OP•2y ago

yeah you helped me, cheers, hahah, in my test i'm creating the relation, then after hitting the endpoint i'm testing it again but i wasn't clearing the tracked values, i presumed once i saved async it was automatically clear 🤦‍♂️ casual 4-6 hours in total time wasted on that

Tvde1•2y ago

I once spent 4 hours trying to figure out why my break point didn't get hit, turns out I was making HTTP calls to the test environment, not to my local api

dave1OP•2y ago

oh yup, done that, more than once or wondering why nothings working because i've left a break point somewhere

Tvde1•2y ago

everyone messes up like that, the trick is that your brain will remember and you'll check stuff much sooner

dave1OP•2y ago

and not noticed, though, not in c#

Tvde1•2y ago

then next time, a colleague asks you for help, you do the sanity checks and you save a lot of time

dave1OP•2y ago

i'm only like 5 days in .net oh, we're switching over to c#, i'm the canary

Tvde1•2y ago

well great job learning Entity Framework so far and making tests!

dave1OP•2y ago

new cto wants to move over, i figure, as long as its not my decision, i'm game, i like learning new systems/languages always tests, first thing i try and figure out how to do when learning a new thing xD it's strange how little literature there is around testing against a TestServer a lot of people saying to just mock EF w/e, but in making an API and basic crud i want to know something is stored.. testcontainers to the rescue anyway, no idea how i'm going to integrate that into the pipeline

Tvde1•2y ago

you're doing this right https://learn.microsoft.com/en-us/aspnet/core/test/integration-tests?view=aspnetcore-7.0

Integration tests in ASP.NET Core

Learn how integration tests ensure that an app's components function correctly at the infrastructure level, including the database, file system, and network.

Tvde1•2y ago

I have yet to dabble with actual integration tests like this

dave1OP•2y ago

i've got two sets one where i inject EF and wrap my tests in transctions, they're my integration the other is using TestServer, where it spins up an instance and i can tests the endpoint, where you cant use transactions, obviously cos it's a different process(coming from a scripting language took me a minute to realise this) a long minute, as once it's built ,it's built, i can't just use the code that's in the request so currently for those webapp tests it spins up a test container per class (testcontainers https://dotnet.testcontainers.org/) it disposes of them after, it's pretty nifty and i can test the system properly, end to end (without the front end) either way, cheers for the help, i was tearing my last few hairs out

Accord•2y 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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❔ Struggling to delete a many to many relation

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