Purpose 

• In app. Run Only terminal middleware delegate is currently being added to the pipeline. 
• app.Use function adds a middleware delegate that is not terminal to the pipeline.

 

Execution:

• app. Run Ends the pipeline after processing the request that was made.
• In app.Use, the request is processed, and then it is sent on to the subsequent middleware element in the pipeline.

 

The end result 

• In app. Run The response is delivered to the client in a direct manner. 
• In app.Use, Context of the request is modified, and then it is passed on to the subsequent middleware. 

 

Felexible 

• app. Run , only deals with the request directly, thus its flexibility is limited. 
• app.Use allows for various middleware components to be chained together, making it more flexible. 

Testing

• app. Run is very difficult to test, because of the terminal nature of the substance.
• The fact that app.Use is a bigger pipeline makes it simpler to test in isolation. 

 

Use cases

• app. Run is suitable for projects that are straightforward and do not require any additional processing.
• app.Use is suitable for extremely complicated applications that call for a number of different processing steps. 

 

Syntax

• app.Run(async context => await context.Response.WriteAsync("…"));
• app.Use.Authentication(); app.Use.Authorization();

 

 

 

Middleware Execution Flow - How MIddleware in Pipeline works in following Use Case

Use case - execution sequence when you have four middlewares added in the order: Use, then Run, then another Use, and finally another Run.

 

In ASP.NET Core, the middleware pipeline processes requests and responses in a specific order. Here's how the execution unfolds with your specified middleware sequence:

• First Use Middleware: This middleware is invoked first. It can perform operations on the incoming request and then call next(), passing control to the next middleware.
• First Run Middleware: This is a terminal middleware. Once invoked, it handles the request and generates a response, terminating the pipeline. No subsequent middleware is executed for this request.
• Second Use Middleware: This middleware is never reached for the current request because the first Run middleware has already terminated the pipeline.  
• Second Run Middleware: Similar to the second Use middleware, this is also never reached for the current request due to the termination by the first Run middleware.