Blazor Server IHttpContextAccessor returning null when deployed

Question

Blazor Server IHttpContextAccessor returning null when deployed

Richard Baker 21

I am dynamically setting the connection string based on the user that is logged in. This is working perfectly when running locally/debugging but when its deployed it's returning a null reference exception. This is my DbContext and I am handling the connection string logic in the OnConfigure method:

namespace SwordfishCRM.Services.ApplicationDbContext  
{  
    public class PrimaryApplicationDbContext : IdentityDbContext<ApplicationUser>  
    {  
        private readonly HttpContext context;  
        private readonly IConfiguration configuration;  
  
        public PrimaryApplicationDbContext(DbContextOptions<PrimaryApplicationDbContext> options, IHttpContextAccessor httpContextAccessor, IConfiguration configuration) : base(options)  
        {  
            this.context = httpContextAccessor.HttpContext;  
            this.configuration = configuration;  
        }  
  
        //Tables  
        public DbSet<Address> Addresses { get; set; }  
        public DbSet<ChimneySweepCycle> ChimneySweepCycles { get; set; }  
        public DbSet<ChimneySweepMethod> ChimneySweepMethods { get; set; }  
        public DbSet<ContactMethod> ContactMethods { get; set; }  
        public DbSet<ContactPreference> ContactPreferences { get; set; }  
        public DbSet<Customer> Customers { get; set; }  
        public DbSet<Diary> Diary { get; set; }  
        public DbSet<DiaryDate> DiaryDates { get; set; }  
        public DbSet<DiaryOption> DiaryOptions { get; set; }  
        public DbSet<Gender> Genders { get; set; }  
        public DbSet<Job> Jobs { get; set; }  
        public DbSet<JobActualLine> JobActualLines { get; set; }  
        public DbSet<JobApproval> JobApprovals { get; set; }  
        public DbSet<JobQuoteLine> JobQuoteLines { get; set; }  
        public DbSet<JobStatus> JobStatuses { get; set; }  
        public DbSet<JobType> JobTypes { get; set; }  
        public DbSet<Product> Products { get; set; }  
        public DbSet<Report> Reports { get; set; }  
        public DbSet<RetroSweepingCertificate> RetroSweepingCertificates { get; set; }  
        public DbSet<ScheduleDay> ScheduleDays { get; set; }  
        public DbSet<ScheduleExceptionDay> ScheduleExceptionDays { get; set; }  
        public DbSet<Title> Titles { get; set; }  
  
        //Views  
        public virtual DbSet<vwAvailableApoointment> vwAvailableApoointments { get; set; }  
  
        protected override void OnModelCreating(ModelBuilder modelBuilder)  
        {  
            base.OnModelCreating(modelBuilder);  
  
            modelBuilder  
                .Entity<vwAvailableApoointment>(eb =>  
                {  
                    eb.HasNoKey();  
                    eb.ToView("vwAvailableApoointments");  
                });  
        }  
  
  
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)  
        {  
            var userId = context.User.Identity.Name;  
            if (userId == null)  
            {  
                optionsBuilder.UseSqlServer(configuration.GetConnectionString("Master"));  
            }  
            else  
            {  
                var prefix = IdentitySupport.GetConnectionPrefix(userId);  
                optionsBuilder.UseSqlServer(configuration.GetConnectionString(prefix));  
            }          
        }  
    }  
}

This is the console error when it's been deployed:

Error: System.NullReferenceException: Object reference not set to an instance of an object.  
   at SwordfishCRM.Services.ApplicationDbContext.PrimaryApplicationDbContext.OnConfiguring(DbContextOptionsBuilder optionsBuilder) in D:\a\1\s\SwordfishCRM.Services\ApplicationDbContext\PrimaryApplicationDbContext .cs:line 67  
   at Microsoft.EntityFrameworkCore.DbContext.get_ContextServices()  
   at Microsoft.EntityFrameworkCore.DbContext.get_Model()  
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.get_EntityType()  
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.CheckState()  
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.get_EntityQueryable()  
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.System.Linq.IQueryable.get_Provider()  
   at System.Linq.Queryable.OrderBy[TSource,TKey](IQueryable`1 source, Expression`1 keySelector)  
   at SwordfishCRM.Web.Pages.Swordfish.DiaryScheduleExceptionDates.OnInitializedAsync() in D:\a\1\s\SwordfishCRM.Web\Pages\Swordfish\DiaryScheduleExceptionDates.razor:line 25  
   at Microsoft.AspNetCore.Components.ComponentBase.RunInitAndSetParametersAsync()

I am confused why this run's locally but not when deployed. I would welcome any support. Thank you

I have tried different variations of HTTPContext but to no avail. I am expecting it to find the logged in user, so I can retrieve a code to set the connection string. There is a fail safe to use the config for the Master database (this is not the actual Master database, just a name for the main database with all the users etc...) There is a step before this that if they are not logged in, they wont even hit this screen.

Locked Question. You can vote on whether it's helpful, but you can't add comments or replies or follow the question.

AgaveJoe 31,706 Reputation points

2023-01-09T18:30:00.397+00:00

Are you sure it worked locally? I ask because Blazor is a client side application and there's no HttpContext except for the very first time the application is downloaded. After that Blazor server uses SignalR to render the content.

https://github.com/dotnet/aspnetcore/issues/17585
Richard Baker 21 Reputation points

2023-01-09T19:58:35.693+00:00

Thank you for your reply, reading the articles, it seems my approach is flawed. What recommendation would you recommend so I can have dynamic connection strings.
Javier López 0 Reputation points

2026-08-26T13:41:32.4666667+00:00
Hi Richard,

The null reference isn't coming from your connection-string logic. It's context itself that's null at line 67. In Blazor Server, IHttpContextAccessor.HttpContext only exists during the initial HTTP request (the prerender). Once the SignalR circuit takes over, and that's what's running when OnInitializedAsync fires your query, there's no HttpContext anymore. So httpContextAccessor.HttpContext comes back null and context.User.Identity.Name throws.

That's also why it runs fine locally but breaks when deployed. It usually comes down to prerendering and render-mode timing. Locally you're probably hitting the path where the request context still exists. Deployed, the interactive circuit runs the query and HttpContext is already gone. Microsoft actually advises against leaning on IHttpContextAccessor in Blazor Server for this exact reason.

Two things you can do:

Quick guard so it stops crashing. Since you capture the context in the constructor, just null-check it: var userId = context?.User?.Identity?.Name; That stops the exception, but it'll quietly fall back to Master for logged-in users too, so treat it as a band-aid rather than the actual fix.

The real fix is to get the user identity the Blazor way, through AuthenticationStateProvider instead of HttpContext. Work out the tenant or connection prefix in a scoped service while the circuit still has auth state, then pass that into the context. An IDbContextFactory pattern fits well here. Now the connection string is picked from an identity source that's actually alive during the interactive phase.
JuliaMarvin 21,425 Reputation points Volunteer Moderator

2026-08-26T15:29:22.76+00:00

@Javier López
Moderator Note
Please refrain from resurrecting old threads. See: [Article] Community Tip: Get the most out of active questions
Also please read https://learn.microsoft.com/en-us/answers/support/ai-usage-policy as well as https://learn.microsoft.com/en-us/answers/support/code-of-conduct

Answer accepted by question author

0 additional answers

AgaveJoe 31,706 Reputation points

2023-01-09T18:30:00.397+00:00

Are you sure it worked locally? I ask because Blazor is a client side application and there's no HttpContext except for the very first time the application is downloaded. After that Blazor server uses SignalR to render the content.

https://github.com/dotnet/aspnetcore/issues/17585
Richard Baker 21 Reputation points

2023-01-09T19:58:35.693+00:00

Thank you for your reply, reading the articles, it seems my approach is flawed. What recommendation would you recommend so I can have dynamic connection strings.
Javier López 0 Reputation points

2026-08-26T13:41:32.4666667+00:00

Hi Richard,

The null reference isn't coming from your connection-string logic. It's context itself that's null at line 67. In Blazor Server, IHttpContextAccessor.HttpContext only exists during the initial HTTP request (the prerender). Once the SignalR circuit takes over, and that's what's running when OnInitializedAsync fires your query, there's no HttpContext anymore. So httpContextAccessor.HttpContext comes back null and context.User.Identity.Name throws.

That's also why it runs fine locally but breaks when deployed. It usually comes down to prerendering and render-mode timing. Locally you're probably hitting the path where the request context still exists. Deployed, the interactive circuit runs the query and HttpContext is already gone. Microsoft actually advises against leaning on IHttpContextAccessor in Blazor Server for this exact reason.

Two things you can do:

Quick guard so it stops crashing. Since you capture the context in the constructor, just null-check it: var userId = context?.User?.Identity?.Name; That stops the exception, but it'll quietly fall back to Master for logged-in users too, so treat it as a band-aid rather than the actual fix.

The real fix is to get the user identity the Blazor way, through AuthenticationStateProvider instead of HttpContext. Work out the tenant or connection prefix in a scoped service while the circuit still has auth state, then pass that into the context. An IDbContextFactory pattern fits well here. Now the connection string is picked from an identity source that's actually alive during the interactive phase.
JuliaMarvin 21,425 Reputation points Volunteer Moderator

2026-08-26T15:29:22.76+00:00

@Javier López
Moderator Note
Please refrain from resurrecting old threads. See: [Article] Community Tip: Get the most out of active questions
Also please read https://learn.microsoft.com/en-us/answers/support/ai-usage-policy as well as https://learn.microsoft.com/en-us/answers/support/code-of-conduct

Answer 1

Bruce (SqlWork.com) 85,111

you should inject the AuthenticationStateProvider instead of context.

Richard Baker 21

Thank you :)

protected override async void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            var authstate = await authenticationStateProvider.GetAuthenticationStateAsync();
            var userId = authstate.User;
            if (userId == null)
            {
                optionsBuilder.UseSqlServer(configuration.GetConnectionString(&#34;Master&#34;));
            }
            else
            {
                var prefix = IdentitySupport.GetConnectionPrefix(userId.Identity.Name);
                await Task.CompletedTask;
                optionsBuilder.UseSqlServer(configuration.GetConnectionString(prefix));
            }        
        }