Aspnetcore.docs: Why use an extension method?

[tompi]

Why not just call UseMiddleware<RequestCultureMiddleware>(); directly on the app?

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Document Details

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• ID: 13e2d968-17a6-1a50-53cd-1d6b9ad0276d
• Version Independent ID: cd22a135-4446-79f5-89db-b741bd44a720
• Content: Write custom ASP.NET Core middleware
• Content Source: aspnetcore/fundamentals/middleware/write.md
• Product: aspnet-core
• Technology: aspnetcore-fundamentals
• GitHub Login: @Rick-Anderson
• Microsoft Alias: riande

[Rick-Anderson]

@serpent5

[serpent5]

Yeah, the extension method is just a wrapper around that call, so both options work. Using an extension method is a convention that's adopted by the built-in middleware components.

Consider a typical middleware pipeline setup that uses endpoint routing, authn, and authz:

app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();
app.UseEndpoints(...);
````

Consider that same configuration without the extension methods:

```csharp
app.UseMiddleware<EndpointRoutingMiddleware>();
app.UseMiddleware<AuthenticationMiddleware>();
app.UseMiddleware<AuthorizationMiddleware>();
app.UseMiddleware<EndpointMiddleware>(...);

There's a lot of noise in that second example, especially around the repeated Middleware. An extension method also allows additional configuration and checks, too. Some of those Use extensions shown above do extra work, such as adding more configuration and verifying that services have been registered.

You certainly don't have to use an extension method, if you don't like the convention and don't have additional configuration needs, etc.

[Rick-Anderson]

Good question and fantastic answer.