instance of entity type cannot be tracked because another instance with same key value is tracked [closed]

This will help you!

AsNoTracking()

By default, EntityFramework tracks changes on entities that are queried and saves changes when you call SaveChanges() on the context.

If it is already tracking product:42, and you add or attach a product with the Id:42 that it hasn't seen, there is ambiguity as to which represents the source of truth.

AsNoTracking produces objects which are not added to the change tracking mechanism, which you should use if you aren't using the change tracking features, because it's faster and makes your intent more explicit.

Most often, this is a scope issue. You don't expect there to be something in the cache, but surprise, there is - usually because of some global variable or a context which was not disposed - Both very common. When you find the offending DbContext, either wrap it in a 'using' or add AsNoTracking.

What difference does .AsNoTracking() make?

In Dotnet 6 you can just add this to your dbcontext options in the program.cs file:

builder.Services.AddDbContext<AppDbContext>(options =>
{
    options.UseSqlServer(connectionString);
    options.UseQueryTrackingBehavior(QueryTrackingBehavior.NoTracking);
});

I ran into this issue, but my DbContext was already registered as Scoped. My issue was that a property was being tracked within a nested navigation property. Nulling that navigation property (leaving the foreign key) fixed this for me.

Just like Rudi Visser suggested, you can face this issue when using one entity across multiple data contexts. In my case, it was something similar to this:

User user = await DataContext.Users.SingleOrDefaultAsync(u => u.Id == "SomeId");

// Switch to UserManager *_*
var res = await UserManager.ResetPasswordAsync(user, token, password); // Exception thrown

A simple solution would be to try to stick to one DataContext, because UserManager seems to do some attaching and detaching (maybe) in the background. For example:

User user = await UserManager.FindByIdAsync("SomeId");
var res = await UserManager.ResetPasswordAsync(user, token, password);

You need Detached Entry-

Entry<CustomerBaseInfo>(data).State = EntityState.Detached;

I am experiencing with same problem and googled and here is my thought

Entity framework has change tracker and entities are stored and referenced in the change tracker using their primary key. More precisely, dbcontext has a secret dictionary and it only allow to store one object of same type and same primary key. It can not track two object of same type and same primary key. Here is my sample code.

var model = new EaEnrollment()
        {
            Id = 1,
            UserId = 2,
            AllocationType = "Individual",
            Status = "In Progress"
        };
        _repoEaEnrollment.Update(model);
        //here is the some other code that meets my businees requirement
        //and changes the status to Completed and trying to update type a

        model.Status = "Completed";
        _repoEaEnrollment.Update(model); // exception .ie. it can not track 
                                         //  two distinct  instance. They are distinct becuase  
                                         //they have same typeand same primary key

I solved by detaching first instance from change tracker. Here is the solution code..

 var model = new EaEnrollment()
        {
            Id = 1,
            UserId = 2,
            AllocationType = "Individual",
            Status = "In Progress"
        };
        _repoEaEnrollment.Update(model);
        _repoEaEnrollment.SaveChanges();
        //here is the some other code that meets my businees requirement
        //and changes the status to Completed and trying to update type a

        //detach first instance from change tracker
        _repoEaEnrollment.Detach(model);

        //Update again
        model.Status = "Completed";
        _repoEaEnrollment.Update(model); // no exception  

In my case I had composite keys (3 keys) in one table and in the configurations I only added 2 of the keys and missed the third one.

Once I added the third key this fixed the issue for me!

I was also facing the same issue. I am on .Net 6.

I was trying to get the entity and was trying to update in the same method. You can add AsNoTracking in your get query and Update like this:

public async Task<Student> GetStudentById(long id, long schoolId)
{
    return await _context.Students.AsNoTracking()
                .FirstOrDefaultAsync(student => student.Id == id && student.SchoolId== schoolId);
}

public async Task<long> UpdateStudent(Student student)
{
    long updatedStudentId = 0;
    var studentInDb = await GetStudentById(student.Id, student.SchoolId);
    if(studentInDb != null)
    {
        _context.Students.Update(student);                
        updatedStudentId = await _context.SaveChangesAsync();
    }
    return updatedStudentId;
}

For me, the following has worked (in .net 6):

dbcontext.Remove(EntityInstance);
dbcontext.model.Update(EntityInstance);

the above has generated the update statement and ran successfully as expected.

the following also has worked:

dbcontext.model.Remove(EntityInstance);
dbcontext.model.Update(EntityInstance);