Explain the difference between app.Run and app.Use in ASP.NET Core.

Question

Aryan Kumar · Answer

The app.run() and app.use() methods are used to configure middleware in ASP.NET Core applications. Middleware is a piece of code that is executed for every request that comes into the application. It can be used to perform tasks such as authentication, authorization, and logging.
The app.run() method is used to configure middleware that will be executed for every request. The
app.use() method is used to configure middleware that will be executed for specific requests.
The main difference between the two methods is that the app.run() method is executed once, at the beginning of the request pipeline, while the
app.use() method is executed multiple times, once for each request that matches the specified route.
Here is an example of how to use the app.run() method to configure middleware that will be executed for every request:
C#
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
namespace MyApp
{
    public class Startup
    {
        public void Configure(IApplicationBuilder app)
        {
            app.Run(async (context) =>
            {
                // This middleware will be executed for every request
                context.Response.Headers.Add("X-Powered-By", "ASP.NET Core");
                await context.Response.WriteAsync("Hello, world!");
            });
        }
    }
}
Here is an example of how to use the app.use() method to configure middleware that will be executed for specific requests:
C#
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
namespace MyApp
{
    public class Startup
    {
        public void Configure(IApplicationBuilder app)
        {
            app.Use(async (context) =>
            {
                // This middleware will be executed for requests that match the '/api/products' route
                if (context.Request.Path == "/api/products")
                {
                    context.Response.Headers.Add("X-API-Product-Version", "1.0");
                }
            });
            app.Run(async (context) =>
            {
                // This middleware will be executed for every request
                context.Response.Headers.Add("X-Powered-By", "ASP.NET Core");
                await context.Response.WriteAsync("Hello, world!");
            });
        }
    }
}
In general, you should use the app.run() method to configure middleware that needs to be executed for every request. You should use the
app.use() method to configure middleware that needs to be executed for specific requests.

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Explain the difference between app.Run and app.Use in ASP.NET Core.

Revati S Misra

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