C#•2w ago

Entity framework overwriting List works?

I always thought that just overwriting a List like solution.Skus = []; doesnt work since the change tracker doesnt update everything, but after some testing it seems to work. Why does everyone then always says to not do this?

        var sku1 = new Sku
        {
            SkuCode = "Sku1",
            Name = "Sku1",
            BusinessCode = "BusinessCode1"
        };
        _newDb.Context.Solutions.Add(new Data.Models.Solution
        {
            Name = "1",
            Skus = [sku1]
        });
        _newDb.Context.Solutions.Add(new Data.Models.Solution
        {
            Name = "2",
            Skus = [sku1]
        });
        await _newDb.Context.SaveChangesAsync();
        _newDb.Context.ChangeTracker.Clear();
        var test1 = await _newDb.Context.Solutions.Include(x => x.Skus).FirstOrDefaultAsync();
        Assert.That(test1.Name, Is.EqualTo("1"));
        Assert.That(test1.Skus.Single().Name, Is.EqualTo("Sku1"));
        test1.Skus = [new Sku
        {
            SkuCode = "Sku2",
            Name = "Sku2",
            BusinessCode = "BusinessCode2"
        }];
        await _newDb.Context.SaveChangesAsync();
        _newDb.Context.ChangeTracker.Clear();
        var test2 = await _newDb.Context.Solutions.Include(x => x.Skus).ToListAsync();
        Assert.That(test2.Single(x => x.Name == "1").Skus.Single().Name, Is.EqualTo("Sku2"));

        var sku1 = new Sku
        {
            SkuCode = "Sku1",
            Name = "Sku1",
            BusinessCode = "BusinessCode1"
        };
        _newDb.Context.Solutions.Add(new Data.Models.Solution
        {
            Name = "1",
            Skus = [sku1]
        });
        _newDb.Context.Solutions.Add(new Data.Models.Solution
        {
            Name = "2",
            Skus = [sku1]
        });
        await _newDb.Context.SaveChangesAsync();
        _newDb.Context.ChangeTracker.Clear();
        var test1 = await _newDb.Context.Solutions.Include(x => x.Skus).FirstOrDefaultAsync();
        Assert.That(test1.Name, Is.EqualTo("1"));
        Assert.That(test1.Skus.Single().Name, Is.EqualTo("Sku1"));
        test1.Skus = [new Sku
        {
            SkuCode = "Sku2",
            Name = "Sku2",
            BusinessCode = "BusinessCode2"
        }];
        await _newDb.Context.SaveChangesAsync();
        _newDb.Context.ChangeTracker.Clear();
        var test2 = await _newDb.Context.Solutions.Include(x => x.Skus).ToListAsync();
        Assert.That(test2.Single(x => x.Name == "1").Skus.Single().Name, Is.EqualTo("Sku2"));

13 Replies

wasabi•2w ago

Because the old list instance may be held elsewhere.

Ancient77OP•2w ago

@wasabi What do you mean by held elsewhere? this is the only code im testing and I tried to clear the changetracker

Unknown User•2w ago

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Ancient77OP•7d ago

ah so I CAN use ef core like that? I always thought / heared that this is not good for ef core

Unknown User•7d ago

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Ancient77OP•7d ago

yea but the problem is its working, when it would expect it to not work, so not really sure how I can find out why that is

Unknown User•7d ago

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Ancient77OP•7d ago

it was just a quick example to show what is happening. I just wanted to clear the changetracker to make sure its not some weird cached state behavior

Unknown User•7d ago

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Ancient77OP•7d ago

I tried to do it with the asserts, but basically everything is working, but I thought you couldn't just replace a list in ef core. In the example I am replacing the test1.Skus with a completely new list, and everything works (the old skus are getting disconnected, and new ones connected). But all the guides always said to not do this, but to use .Add() .Remove() .Clear()

Unknown User•7d ago

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blinkbat•7d ago

state tracking is more trouble than it's worth IMO just assemble your dtos and fire the needed queries

Unknown User•7d ago

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Entity framework overwriting List works?

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