How to pass primitive data to asp.net core middleware

Question

I need to pass some data into a ASP NET CORE middleware

eg if this is a list of strings, do you use the same mechanism as passing in a service?

eg add it as a parameter to the Invoke method and register it with the DI?

If so, how do you do the registration for primitive types? eg a lsit of strings. does it have to be a named type or something like that?

Or can we pass the data in some other way?

thanks

Answer 1

Let's suppose we have a middleware:

public class FooMiddleware
{
    public FooMiddleware(RequestDelegate next, List<string> list)
    {
        _next = next;
    }
}

Just pass a list to UseMiddleware call to resolve it per-middleware :

app.UseMiddleware<FooMiddleware>(new List<string>());

You could create a DTO and pass it:

public FooMiddleware(RequestDelegate next, Payload payload)
....
app.UseMiddleware<FooMiddleware>(new Payload());    

Or register this DTO in DI container, it will be resolved in middleware:

public void ConfigureServices(IServiceCollection services)
{
    services.AddSingleton<Payload>(new Payload());
}

In addition, DI container allows to resolve per-request dependencies:

public async Task Invoke(HttpContext httpContext, IMyScopedService svc)
{
    svc.MyProperty = 1000;
    await _next(httpContext);
}

Documentation:

Because middleware is constructed at app startup, not per-request, scoped lifetime services used by middleware constructors are not shared with other dependency-injected types during each request. If you must share a scoped service between your middleware and other types, add these services to the Invoke method's signature. The Invoke method can accept additional parameters that are populated by dependency injection.