C#•4d ago

DbConcurrencyException, what am I missing?

Hi, getting this on the SaveChangesAsync and im not really sure what im doing wrong. DbConcurrencyException: The database operation was expected to affect 1 row(s), but actually affected 0 row(s); data may have been modified or deleted since entities were loaded. Inside UserService.cs:

 public async Task SetVariable(Guid productId, Guid userId, string requestKey, string requestValue)
    {
        var product = await productRepository.GetByIdAsync(productId);
        if (product is null)
        {
            throw new ProductNotFoundException(productId);
        }

        var user = await userRepository.GetByIdAsync(productId, userId);
        if (user is null)
        {
            throw new UserNotFoundException(userId);
        }

        user.SetVariable(requestKey, requestValue);
        userRepository.Update(user);
        await unitOfWork.SaveChangesAsync();
    }

 public async Task SetVariable(Guid productId, Guid userId, string requestKey, string requestValue)
    {
        var product = await productRepository.GetByIdAsync(productId);
        if (product is null)
        {
            throw new ProductNotFoundException(productId);
        }

        var user = await userRepository.GetByIdAsync(productId, userId);
        if (user is null)
        {
            throw new UserNotFoundException(userId);
        }

        user.SetVariable(requestKey, requestValue);
        userRepository.Update(user);
        await unitOfWork.SaveChangesAsync();
    }

Inside User.cs:

    public ICollection<UserVariable> Variables { get; set; }

    public void SetVariable(string key, string value)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(key);

        var existingVariable = Variables.FirstOrDefault(v => v.Key.Equals(key, StringComparison.OrdinalIgnoreCase));

        if (existingVariable != null)
        {
            existingVariable.UpdateValue(value);
        }
        else
        {
            var newVariable = UserVariable.Create(Guid.NewGuid(), Id, key, value);
            Variables.Add(newVariable);
        }
    }

    public ICollection<UserVariable> Variables { get; set; }

    public void SetVariable(string key, string value)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(key);

        var existingVariable = Variables.FirstOrDefault(v => v.Key.Equals(key, StringComparison.OrdinalIgnoreCase));

        if (existingVariable != null)
        {
            existingVariable.UpdateValue(value);
        }
        else
        {
            var newVariable = UserVariable.Create(Guid.NewGuid(), Id, key, value);
            Variables.Add(newVariable);
        }
    }

Inside UserRepository.cs:

    public void Update(User user)
    {
        dbContext.Set<User>().Update(user);
    }

    public void Update(User user)
    {
        dbContext.Set<User>().Update(user);
    }

32 Replies

JuicyOP•4d ago

Also to mention, I do include Variables when getting the user and I also tried without the explicit Update call

Angius•4d ago

I generally avoid using .Update() And using repositories, but that's another matter See if using .ExecuteUpdateAsync() would fix the issue

Jimmacle•4d ago

ah, the joys of wrapping EF in generic repositories

JuicyOP•4d ago

😭

Jimmacle•4d ago

which you shouldn't if you have a choice

JuicyOP•4d ago

Why do "best practices" youtube channels teach this stuff

Jimmacle•4d ago

¯\_(ツ)_/¯ lots of useless content out there

JuicyOP•4d ago

anyway

  dbContext.Set<User>().ExecuteUpdateAsync(
            u => u.SetProperty(x => x.Variables, user.Variables));

  dbContext.Set<User>().ExecuteUpdateAsync(
            u => u.SetProperty(x => x.Variables, user.Variables));

is this how you use it? It doesnt seem to work

Jimmacle•4d ago

that would set those variables on every single user in the table you didn't filter it beforehand

JuicyOP•4d ago

Jimmacle•4d ago

i'm not actually sure how executeupdate works with navigation properties, i haven't tried it

JuicyOP•4d ago

is there another possible way I could fix the issue?

Jimmacle•4d ago

as far as options go, you can load, modify, then save the user and let the change tracker deal with it if you can tolerate the performance penalty of 2 round trips

JuicyOP•4d ago

yeah this isnt very performance dependant thats kinda what I tried to do I guess loading the user, modifying it's Variables collection and then trying to save the user

Jimmacle•4d ago

you don't need to use Update if the object is already being tracked by the dbcontext

JuicyOP•4d ago

yeah that makes sense but UserVariable has its own table as well

Jimmacle•4d ago

that's fine, the change tracker can deal with that

JuicyOP•4d ago

But even without the Update its giving me the DbUpdateConcurrencyException It feels like it should work..?

[16:18:59 INF] Executed DbCommand (1ms) [Parameters=[@p3='?' (DbType = Guid), @p0='?' (Size = 64), @p1='?' (DbType = Guid), @p2='?' (Size = 512)], CommandType='Text', CommandTimeout='30']
SET IMPLICIT_TRANSACTIONS OFF;
SET NOCOUNT ON;
UPDATE [UserVariables] SET [Key] = @p0, [UserId] = @p1, [Value] = @p2
OUTPUT 1
WHERE [Id] = @p3;

[16:18:59 INF] Executed DbCommand (1ms) [Parameters=[@p3='?' (DbType = Guid), @p0='?' (Size = 64), @p1='?' (DbType = Guid), @p2='?' (Size = 512)], CommandType='Text', CommandTimeout='30']
SET IMPLICIT_TRANSACTIONS OFF;
SET NOCOUNT ON;
UPDATE [UserVariables] SET [Key] = @p0, [UserId] = @p1, [Value] = @p2
OUTPUT 1
WHERE [Id] = @p3;

Jimmacle•4d ago

are you somehow changing the ID of the user (or variable) either in the entity or in the db in the middle of this happening?

JuicyOP•4d ago

yes the variable is recieving a new ID

   var newVariable = UserVariable.Create(Guid.NewGuid(), Id, key, value);

   var newVariable = UserVariable.Create(Guid.NewGuid(), Id, key, value);

Jimmacle•4d ago

so you need to insert, not update

JuicyOP•4d ago

using System.ComponentModel.DataAnnotations;

namespace Lightning.Domain.Models;

public sealed class UserVariable : BaseEntity
{
    private const int MaxKeyLength = 64;
    private const int MaxValueLength = 256;
    private UserVariable(Guid id, Guid userId, string key, string? value) : base(id)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(key, nameof(key));
        if (key.Length > MaxKeyLength)
        {
            throw new ArgumentException($"Key length exceeds {MaxKeyLength} characters.", nameof(key));
        }
        if (value?.Length > MaxValueLength)
        {
            throw new ArgumentException($"Value length exceeds {MaxValueLength} characters.", nameof(value));
        }
        
        UserId = userId;
        Key = key;
        Value = value;
    }
    

    [MaxLength(MaxKeyLength)] public string Key { get; private set; }
    [MaxLength(MaxValueLength)] public string? Value { get; private set; }
    
    public Guid UserId { get; private set; }
    public User User { get; private set; } = null!;
    
    public static UserVariable Create(Guid id, Guid userId, string key, string? value)
    {
        return new UserVariable(id, userId, key, value);
    }
    
    public void UpdateValue(string? newValue)
    {
        if (newValue?.Length > MaxValueLength)
        {
            throw new ArgumentException($"Value length exceeds {MaxValueLength} characters.", nameof(newValue));
        }
        Value = newValue;
    }
}

using System.ComponentModel.DataAnnotations;

namespace Lightning.Domain.Models;

public sealed class UserVariable : BaseEntity
{
    private const int MaxKeyLength = 64;
    private const int MaxValueLength = 256;
    private UserVariable(Guid id, Guid userId, string key, string? value) : base(id)
    {
        ArgumentException.ThrowIfNullOrWhiteSpace(key, nameof(key));
        if (key.Length > MaxKeyLength)
        {
            throw new ArgumentException($"Key length exceeds {MaxKeyLength} characters.", nameof(key));
        }
        if (value?.Length > MaxValueLength)
        {
            throw new ArgumentException($"Value length exceeds {MaxValueLength} characters.", nameof(value));
        }
        
        UserId = userId;
        Key = key;
        Value = value;
    }
    

    [MaxLength(MaxKeyLength)] public string Key { get; private set; }
    [MaxLength(MaxValueLength)] public string? Value { get; private set; }
    
    public Guid UserId { get; private set; }
    public User User { get; private set; } = null!;
    
    public static UserVariable Create(Guid id, Guid userId, string key, string? value)
    {
        return new UserVariable(id, userId, key, value);
    }
    
    public void UpdateValue(string? newValue)
    {
        if (newValue?.Length > MaxValueLength)
        {
            throw new ArgumentException($"Value length exceeds {MaxValueLength} characters.", nameof(newValue));
        }
        Value = newValue;
    }
}

Jimmacle•4d ago

if you change the ID then WHERE [Id] = @p3; is never going to find the old one

JuicyOP•4d ago

ah but thats weird so I need to insert the userVariable to it's table before I add it to the user collection

Jimmacle•4d ago

no, it basically means you're doing something in your EF model that is leading it to generate the wrong SQL for what actually needs to happen

JuicyOP•4d ago

i see I honestly have no clue what it could be In the other cases I have repositories for every model that im working with so I just add it via reposistory before adding it to another model's collection but in this case I thought it would be unnecessary how can I check if its handled by change tracker btw?

Jimmacle•4d ago

if you got the object from a query on the same dbcontext (that didn't use AsNoTracking), explicitly added it with Add, or is a member of an object that meets those conditions, it's handled by the change tracker

JuicyOP•4d ago

ah yeah I just get it like this

    public async Task<User?> GetByIdAsync(Guid productId, Guid id, CancellationToken cancellationToken = default)
    {
        return await dbContext.Set<User>()
            .Include(u => u.Licenses)
            .Include(u => u.Machine)
            .Include(u => u.Variables)
            .FirstOrDefaultAsync(u => u.ProductId == productId && u.Id == id, cancellationToken);
    }

    public async Task<User?> GetByIdAsync(Guid productId, Guid id, CancellationToken cancellationToken = default)
    {
        return await dbContext.Set<User>()
            .Include(u => u.Licenses)
            .Include(u => u.Machine)
            .Include(u => u.Variables)
            .FirstOrDefaultAsync(u => u.ProductId == productId && u.Id == id, cancellationToken);
    }

Jimmacle•4d ago

then all you should have to do is add to the user's variables collection and call savechanges, you don't even need to explicitly set the reference to the user

JuicyOP•4d ago

damn

Jimmacle•4d ago

the change tracker will figure that out if it sees a new item in the user's variables collection

JuicyOP•4d ago

could it be the way i configured the table? i have no clue how to find the issue 😭 I tried to drop the database and have EF core re create it but still same Well I found the cause Value generation was turned on even though I set the Id property manually on creation so I had to add a .ValueGeneratedNever() alternatively had to manually insert by calling DbContext.Add but since I handle the id creations myself I just set the .ValueGeneratedNever and now it seems to work fine

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