Ztere0 Ztere0 - 11 months ago 51
C# Question

EF7 beta6: Error saving multiple entities

I am creating an API using ASP.NET5 and Entity Framework 7.0.0-beta 6, and when I try to execute various updates in several requests, I get this Exception:

'Company' cannot be tracked because another instance of this type with the same key is already being tracked. For new entities consider using an IIdentityGenerator to generate unique key values.

This is my code:

public class MrBellhopContext : DbContext

public DbSet<Company> Company { get; set; }

protected override void OnModelCreating(ModelBuilder modelBuilder)
modelBuilder.Entity<Company>(entity =>
entity.Key(c => c.CompanyId);

entity.Index(c => c.Name);

entity.Property(c => c.CompanyId).ValueGeneratedOnAdd();




public class Company

public int CompanyId { get; set; }

public string Name { get; set; }

public string Description { get; set; }

public string Phone { get; set; }

public string Email { get; set; }

public short StatusId { get; set; }


public class CompanyRepository : ICompanyRepository

MrBellhopContext _dbcontext;

public async Task UpdateAsync(Company company)
await _dbcontext.SaveChangesAsync();

public class CompanyController : Controller

public async void UpdateAsync([FromBody] Company company)
if ((!ModelState.IsValid) || (company == null))
Context.Response.StatusCode = 400;
await _repository.UpdateAsync(company);


I have tried to solve it by removing ValueGeneratedOnAdd(), UseSqlServerIdentityColumns() or changing the mapping, but if I try to update several entities in several requests, I get the Exception:

  1. First req: Update CompanyId 8

  2. First req: Update CompanyId 9 !! ERROR

Does anyone know how to solve this issue?

Answer Source

Resolved: https://github.com/aspnet/EntityFramework/issues/2652

I was adding Repository as a Singleton:


This means that all requests are sharing a single instance of the repository. You should reduce this to Scoped, so that you have a single repository instance per request. Aside from avoiding the issue you are hitting, it will also ensure you don't end up with a gigantic context instance tracking all the data from your database in memory.

To solve: