Multilingual site content issue

JafferHussain · October 7, 2026, 7:07am

I am facing an issue with a multilingual site setup in Umbraco 17. The same setup was working correctly in Umbraco 13. The only significant change is that Nested Content, which I was using in Umbraco 13, has been deprecated in Umbraco 17. As a result, I replaced it with Umbraco.Cms.Core.Models.Blocks.BlockListModel. However, after migrating from Umbraco 13 to Umbraco 17, I started experiencing the following issue.

I have configured BlockListModel content for both languages (en-US and es-PR), with en-US set as the default language.

The cultures and hosts are configured as follows:

http://www.siteurl.com → es-PR site
http://www.siteurl.com/en-us → en-US site

The http://www.siteurl.com site works as expected. After publishing content, the http://www.siteurl.com/en-us site initially returns the BlockListModel content correctly. However, after some time, when I revisit the site, the BlockListModel content is no longer returned properly.

Could you please help me understand what might be causing this issue in Umbraco 17 and how it can be resolved? Has anyone encountered a similar issue related to multilingual content, caching, or Block List localization after migrating from Nested Content to BlockListModel?

getting below exception
System.NullReferenceException: Object reference not set to an instance of an object.
at AspNetCoreGeneratedDocument.Views_Partials_page.ExecuteAsync()
at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageCoreAsync(IRazorPage page, ViewContext context)
at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageAsync(IRazorPage page, ViewContext context, Boolean invokeViewStarts)
at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderAsync(ViewContext context)
at Microsoft.AspNetCore.Mvc.ViewFeatures.HtmlHelper.RenderPartialCoreAsync(String partialViewName, Object model, ViewDataDictionary viewData, TextWriter writer)
at Microsoft.AspNetCore.Mvc.ViewFeatures.HtmlHelper.PartialAsync(String partialViewName, Object model, ViewDataDictionary viewData)
at Microsoft.AspNetCore.Mvc.Rendering.HtmlHelperPartialExtensions.Partial(IHtmlHelper htmlHelper, String partialViewName)
at AspNetCoreGeneratedDocument.Views_Partials_Homepage.ExecuteAsync()
at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageCoreAsync(IRazorPage page, ViewContext context)
at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageAsync(IRazorPage page, ViewContext context, Boolean invokeViewStarts)
at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderAsync(ViewContext context)
at Microsoft.AspNetCore.Mvc.ViewFeatures.HtmlHelper.RenderPartialCoreAsync(String partialViewName, Object model, ViewDataDictionary viewData, TextWriter writer)
at Microsoft.AspNetCore.Mvc.ViewFeatures.HtmlHelper.PartialAsync(String partialViewName, Object model, ViewDataDictionary viewData)
at Microsoft.AspNetCore.Mvc.Rendering.HtmlHelperPartialExtensions.Partial(IHtmlHelper htmlHelper, String partialViewName)
at AspNetCoreGeneratedDocument.Views_SiteSettingsVertical.ExecuteAsync()
at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageCoreAsync(IRazorPage page, ViewContext context)
at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderPageAsync(IRazorPage page, ViewContext context, Boolean invokeViewStarts)
at Microsoft.AspNetCore.Mvc.Razor.RazorView.RenderAsync(ViewContext context)
at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, String contentType, Nullable1 statusCode) at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ViewContext viewContext, String contentType, Nullable1 statusCode)
at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewExecutor.ExecuteAsync(ActionContext actionContext, IView view, ViewDataDictionary viewData, ITempDataDictionary tempData, String contentType, Nullable`1 statusCode)
at Microsoft.AspNetCore.Mvc.ViewFeatures.ViewResultExecutor.ExecuteAsync(ActionContext context, ViewResult result)
at Microsoft.AspNetCore.Mvc.ViewResult.ExecuteResultAsync(ActionContext context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Logged|22_0(ResourceInvoker invoker, IActionResult result)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|30_0[TFilter,TFilterAsync](ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResultExecutedContextSealed context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.ResultNext[TFilter,TFilterAsync](State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeResultFilters()
— End of stack trace from previous location —
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Awaited|25_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, Object state, Boolean isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(State& next, Scope& scope, Object& state, Boolean& isCompleted)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
— End of stack trace from previous location —
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Logged|17_1(ResourceInvoker invoker)
at Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.g__Logged|17_1(ResourceInvoker invoker)
at Umbraco.Cms.Web.Common.Middleware.BasicAuthenticationMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<b__0>d.MoveNext()
— End of stack trace from previous location —
at Umbraco.Cms.Api.Management.Middleware.BackOfficeExternalLoginProviderErrorMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<b__0>d.MoveNext()
— End of stack trace from previous location —
at Swashbuckle.AspNetCore.SwaggerUI.SwaggerUIMiddleware.Invoke(HttpContext httpContext)
at Swashbuckle.AspNetCore.Swagger.SwaggerMiddleware.Invoke(HttpContext httpContext, ISwaggerProvider swaggerProvider)
at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Localization.RequestLocalizationMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Authorization.AuthorizationMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
at Umbraco.Cms.Web.Common.Middleware.ProtectRecycleBinMediaMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<b__0>d.MoveNext()
— End of stack trace from previous location —
at StackExchange.Profiling.MiniProfilerMiddleware.Invoke(HttpContext context) in C:\projects\dotnet\src\MiniProfiler.AspNetCore\MiniProfilerMiddleware.cs:line 112
at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<b__0>d.MoveNext()
— End of stack trace from previous location —
at Umbraco.Cms.Web.Common.Middleware.PreviewAuthenticationMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<b__0>d.MoveNext()
— End of stack trace from previous location —
at Umbraco.Cms.Web.Common.Middleware.BootFailedMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<b__0>d.MoveNext()
— End of stack trace from previous location —
at Umbraco.Cms.Web.Common.Middleware.UmbracoRequestLoggingMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<b__0>d.MoveNext()
— End of stack trace from previous location —
at SixLabors.ImageSharp.Web.Middleware.ImageSharpMiddleware.Invoke(HttpContext httpContext, Boolean retry)
at Umbraco.Cms.Api.Management.Middleware.BackOfficeAuthorizationInitializationMiddleware.InvokeAsync(HttpContext context, RequestDelegate next)
at Microsoft.AspNetCore.Builder.UseMiddlewareExtensions.InterfaceMiddlewareBinder.<>c__DisplayClass2_0.<b__0>d.MoveNext()
— End of stack trace from previous location —
at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
at Microsoft.AspNetCore.Diagnostics.DeveloperExceptionPageMiddlewareImpl.Invoke(HttpContext context)

justin-nevitech · October 7, 2026, 7:11am

Hi @JafferHussain

When this happens, what does the Block List property look like in the CMS? Can you see the en-US and es-PR property data and does it look normal? What then happens if you re-publish the page, does that fix it until it breaks again later?

When you say the BlockListModel content is no longer returned properly, what happens? Do you get an error?

Also, how did you migrate from Nested Content to Block List?

Justin

JafferHussain · October 7, 2026, 8:15am

Hi Justin,

Yes, the en-US and es-PR property data always look normal. This issue happened on and off. Sometimes I am getting the Block List content properly, and sometimes I am getting a null reference exception.
Manually replaced the Nested Content with the Block List property

justin-nevitech · October 7, 2026, 8:24am

Hi @JafferHussain

And if you re-publish, does that solve the problem until the next time?

Justin

JafferHussain · October 7, 2026, 12:39pm

yes. After re publishing it works

justin-nevitech · October 7, 2026, 1:07pm

Hi @JafferHussain

Thanks, the fact that re-publishing fixes it is a good clue. In v17 a publish rebuilds the cached page directly from the content, but when the cache entry expires or the site restarts it’s rebuilt from the database cache instead, so it sounds like the en-US value isn’t surviving that second route.

Could you try going to Settings > Published Status, rebuilding the database cache, then restarting the site and going straight to /en-us? If it fails straight away, that confirms it and gives you a reliable way to reproduce it.

A few more questions:

When you say you manually replaced Nested Content, did you change the data type on the existing property, or create a new Block List property and re-enter the content?
Is the Block List property set to vary by culture, and are the properties on the element types set to vary by culture?
Can you share the code in page.cshtml around where you read the Block List, so we can see which object is null?

Justin (with the help of AI)