Resolving the "An error occurred while accessing the Microsoft.Extensions.Hosting services" in ASP.NET Core

Introduction:

When working with ASP.NET Core, you may encounter an error message stating "An error occurred while accessing the Microsoft.Extensions.Hosting services." This error often occurs when there are issues with service registration or configuration. One specific error scenario that can lead to this message is related to the use of the `AddDistributedSession` method in the `IServiceCollection`. This blog post will guide you through the process of resolving this error and configuring session options using the correct method, `AddSession`.

Step 1: Understanding the error message

The error message "An error occurred while accessing the Microsoft.Extensions.Hosting services" indicates that there are problems with the services being constructed and resolved within the ASP.NET Core application. In this case, the error is related to the session configuration.

Step 2: Identifying the issue

The specific error message you encountered includes the following information: "Unable to resolve service for type 'Microsoft.Extensions.Caching.Distributed.IDistributedCache' while attempting to activate 'Microsoft.AspNetCore.Session.DistributedSessionStore'." This error suggests that there is a missing or incorrectly configured service related to distributed caching.

Step 3: Solution

To resolve the error and correctly configure session options, follow these steps:

1. Open your application's startup class, typically named `Startup.cs`.

2. Ensure that you have the necessary using directives:

   ```csharp

   using Microsoft.AspNetCore.Builder;

   using Microsoft.Extensions.DependencyInjection;

   ```

3. Locate the `ConfigureServices` method within the startup class.

4. Replace the `AddDistributedSession` method with `AddSession` to configure session options:

   ```csharp

   services.AddDistributedMemoryCache();

   services.AddSession(options =>

   {

       // Set the session timeout (optional)

       options.IdleTimeout = TimeSpan.FromMinutes(20); // Example: Set session timeout to 20 minutes

       // Configure the cookie settings (optional)

       options.Cookie.Name = "MySessionCookie"; // Example: Set a custom cookie name

       options.Cookie.HttpOnly = true; // Example: Set the cookie to be accessible only through HTTP

       options.Cookie.SecurePolicy = CookieSecurePolicy.Always; // Example: Enforce secure cookies over HTTPS

       // Configure other session options as needed

       // options.Cookie.IsEssential = true; // Example: Mark the session cookie as essential

   });

   ```

5. Make sure you have the necessary package installed: `Microsoft.AspNetCore.Session`. If it's not already installed, you can add it using the NuGet package manager.

6. Build and run your application to verify that the error has been resolved.

Conclusion:

By following the steps outlined in this blog post, you should be able to resolve the "An error occurred while accessing the Microsoft.Extensions.Hosting services" error in your ASP.NET Core application. Additionally, you have learned how to correctly configure session options using the `AddSession` method. Remember to pay attention to the error messages and examine them carefully to identify the root cause of the issue.