How to know the user edited? - entity-framework-core

Question

I am using Blazor server-side with ASP.NET Core 5 and EF Core 5. I would like that when a record is updated than the ModifiedBy and CreatedBy are generated automatically.
I have overriden SaveChangeAsync as follows:
public override Task<int> SaveChangesAsync(CancellationToken cancellationToken = default)
{
ApplyInterfaces();
return base.SaveChangesAsync(cancellationToken);
}
private void ApplyInterfaces()
{
var userId = _httpContextAccessor?.HttpContext?.User?.Identity?.Name;
var currentUsername = !string.IsNullOrEmpty(userId)? userId: "Anonymous";
foreach (ICreatedBy entity in ChangeTracker.Entries().Where(x => x.Entity is ICreatedBy).Where(x => x.State == EntityState.Added).Select(x=> x.Entity))
{
entity.CreatedBy = currentUsername;
entity.CreatedDate = DateTime.Now;
}
foreach (IModifiedBy entity in ChangeTracker.Entries().Where(x=> x.State == EntityState.Modified).Where(x => x.Entity is IModifiedBy).Select(x => x.Entity))
{
entity.ModifiedBy = currentUsername;
entity.ModifiedDate = DateTime.Now;
}
}
_httpContextAccessor is injected to the DBContext. I added the services
services.AddHttpContextAccessor();
Everything works fine on IIS Express. But when I publish to IIS _httpContextAccessor.HttpContext is null.
Where did I miss something?

Answer 1

You should not use IHttpContextAccessor in Blazor apps (source).
It's not clear from your code sample if this code is in a Blazor component/page or in a database access library. If it's in the database layer you should modify SaveChangesAsync to add a string username parameter, which you can then pass to ApplyInterfaces.
Getting the user should be the responsibility of the Blazor page/component, using either AuthenticationStateProvider or an AuthorizeView component.
#page "/example"
#inject AuthenticationStateProvider auth;
<button #OnClick="Save">Save</button>
#code
{
async Task Save()
{
var state = await auth.GetAuthenticationStateAsync();
var username = state.User.Identity?.Name ?? "[anon]";
await someObject.SaveChangesAsync(username);
}
}