What is middleware and multiple ways to create middleware in .NET Core ?

What is middleware ?
Middleware is a software assembled into an app pipeline to handle request and response.
In simple words middleware gives us the facility to add additional logic before and after the HTTP request.
How middleware works ?

Suppose we have three middlewares in our app then for each middleware we enter two time.

• First middleware logic is performed then we send it to next middleware

• Secondly when request comes back after executing the next middlewares
  Multiple ways of creating middlewares
  We have three ways to create middleware in .NET Core

• Request delegate (Most simple)

• By convention

• Using middleware factory
  Creating middleware using Request Delegate
  In this way we can create middleware using app.Use in our Program.cs

We can add our logic that we want to perform before or after this middleware.

If you don’t want to call next middleware we can achieve that by not invoking next.

Our Program.cs file would look like this :

To learn more about this technique visit Microsoft Docs

Creating middleware by Convention
It has three steps :

• Create a class of your middleware and pass RequestDelegate in its constructor.
• Now add a method responsible for logic before and after the middleware, pass it HttpContext
• Add middleware in Program.cs After first two step our code would be like :

Tell the Program.cs about this middleware by using app.UseMiddleware<name>()

Creating middleware using Factory
This is modified version of conventional way , in this we create our class and inherit it from IMiddleware. In this way IMiddleware enforces us to implement InvokeAsync method. So the code looks like :

One last step is to informing Program.cs about this middleware , but this time we can not do it only with app.UseMiddleware , we have to add it in built-in DI container. We have to register its service as well like this :

The factory method is most appreciated by developers because it has less chance of error and it is more clean.

Explore more about last two approaches from Microsoft Docs.