In the last few posts I have been writing about ASP.NET Core middlewares. You have seen how to create one, pass data from request and setup dependency injection. Today I would like to show you, how you can build a configuration for the middleware and set it up from the Startup class.

Implementation

In the Stactive project, I want to be able to decide which modules should be used, or where the data should be stored. The best place for such setup is the ConfigureServices method of the Startup class. That’s how it’s done for EntityFramework and IdentityFramework:

services.AddDbContext<ApplicationDbContext>(options =>
    options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));

services.AddIdentity<ApplicationUser, IdentityRole>()
    .AddEntityFrameworkStores<ApplicationDbContext>()
    .AddDefaultTokenProviders();

As you can see, they use two methods. EntityFramework is using an options builder - you get an options object and set it up to your needs. IdentityFramework uses few extension methods on the services object to setup various options. I prefer the first solution - I think it’s cleaner and would like to use in Stactive project.

First, we need to create a StactiveOptions class, which will contain all the settings. For the first implementation, I have just added a bool field UseMongoDb:

public class StactiveOptions
{
    internal bool UseMongoDb { get; set; }
}

Next, we need a static field in the Stactive object - a place where we will keep our configuration:

internal static StactiveOptions Options { get; } = new StactiveOptions();

As you see it’s marked as internal, so that it’s available for other components of the library and is initialized with an empty object.

Now, we need an options builder class:

public static class StactiveOptionsBuilder
{
    public static StactiveOptions UseMongoDb(this StactiveOptions options)
    {
        options.UseMongoDb = true;
        return options;
    }
}

For now, it contains one extension method, which just sets the bool field to true. Later on, it should take a connection string to the database and write it down.

At this point we have everything we need to configure Stactive from the Startup class:

services.AddStactive(options => options.UseMongoDb());

Summary

I hope you will find this short post useful. It’s a quick and dirty implementation, but does the job and can be improved later. If you have a better way to setup middlewares, please share in comments. Whole commit for this change is available on GitHub.