Kolya_Net Kolya_Net - 1 year ago 265
C# Question

How to add IHttpContextAccessor in the Startup class in the DI in ASP.NET Core 1.0?

In ASP.NET Core RC 1 I used the following code to retrieve the value of context (full address of the page). Then I recorded this value in the configuration.

public class Startup
{
public IConfigurationRoot Configuration { get; set; }
private IHostingEnvironment CurrentEnvironment { get; set; }
private IHttpContextAccessor HttpContextAccessor { get; set; }
public Startup(IHostingEnvironment env,
IHttpContextAccessor httpContextAccessor)
{
var builder = new ConfigurationBuilder()
.SetBasePath(env.ContentRootPath)
.AddJsonFile("appsettings.json", optional: true, reloadOnChange: true)
.AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: true);

if (env.IsDevelopment())
{
builder.AddUserSecrets();
}
builder.AddEnvironmentVariables();
Configuration = builder.Build();
CurrentEnvironment = env;
HttpContextAccessor = httpContextAccessor;
}
public void ConfigureServices(IServiceCollection services)
{
...

services.AddOptions();
services.Configure<WebAppSettings>(configuration);
services.Configure<WebAppSettings>(settings =>
{
...
settings.WebRootPath = CurrentEnvironment.WebRootPath;
settings.DomainUrl = HttpContextAccessor.HttpContext.Request.Host.ToUriComponent();
});
}
}


Now I started to update the project on ASP.NET Core 1.0. But during the launch of the site I get the following error:


System.InvalidOperationException Unable to resolve service for type
'Microsoft.AspNetCore.Http.IHttpContextAccessor' while attempting to
activate 'MyProject.Startup'.

at
Microsoft.Extensions.Internal.ConstructorMatcher.CreateInstance(IServiceProvider
provider) at
Microsoft.Extensions.Internal.ActivatorUtilities.CreateInstance(IServiceProvider
provider, Type instanceType, Object[] parameters) at
Microsoft.Extensions.Internal.ActivatorUtilities.GetServiceOrCreateInstance(IServiceProvider
provider, Type type) at
Microsoft.Extensions.DependencyInjection.ActivatorUtilities.GetServiceOrCreateInstance(IServiceProvider
provider, Type type) at
Microsoft.AspNetCore.Hosting.Internal.StartupLoader.LoadMethods(IServiceProvider
services, Type startupType, string environmentName) at
Microsoft.AspNetCore.Hosting.<>c__DisplayClass1_0.b__1(IServiceProvider
sp) at
Microsoft.Extensions.DependencyInjection.ServiceLookup.FactoryService.Invoke(ServiceProvider
provider) at
Microsoft.Extensions.DependencyInjection.ScopedCallSite.Invoke(ServiceProvider
provider) at
Microsoft.Extensions.DependencyInjection.SingletonCallSite.Invoke(ServiceProvider
provider) at
Microsoft.Extensions.DependencyInjection.<>c__DisplayClass12_0.b__0(ServiceProvider
provider) at
Microsoft.Extensions.DependencyInjection.ServiceProvider.GetService(Type
serviceType) at
Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider
provider, Type serviceType) at
Microsoft.Extensions.DependencyInjection.ServiceProviderServiceExtensions.GetRequiredService(IServiceProvider
provider) at
Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureStartup() at
Microsoft.AspNetCore.Hosting.Internal.WebHost.EnsureApplicationServices()
at Microsoft.AspNetCore.Hosting.Internal.WebHost.BuildApplication()

.NET Framework X64 v4.0.30319.42000 | Microsoft.AspNetCore.Hosting
version 1.0.0-rtm-21431 | Microsoft Windows 6.1.7601 S


How do I get the new version IHttpContextAccessor during application startup?

Answer Source

It is not longer a default service. You have to configure it in Startup.cs

services.TryAddSingleton<IHttpContextAccessor, HttpContextAccessor>();
services.TryAddSingleton<IActionContextAccessor, ActionContextAccessor>();

UPDATE: In ASP.NET Core 2.1, the AddHttpContextAccessor helper extension method was added to correctly register the IHttpContextAccessor with the correct lifetime (singleton). So, in ASP.NET Core 2.1 and above, the code should be

services.AddHttpContextAccessor();
services.TryAddSingleton<IActionContextAccessor, ActionContextAccessor>();

Source: https://github.com/aspnet/Hosting/issues/793

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