How deeply does Building Web APIs with ASP.NET Core cover CORS middleware?

Shows policy registration and middleware placement, then contrasts global application with endpoint-level alternatives.

CORS middleware

As explained in Building Web APIs with ASP.NET Core

CORS middleware is an HTTP pipeline component that applies cross-origin request policies to web API requests and responses.

CORS middleware applies a cross-origin policy across an ASP.NET Core app. It is the simplest choice when the board-game API should use the same default policy for its controllers and Minimal API endpoints. section 3.1.1

// ...
 
app.UseCors();
 
app.UseAuthorization();
 
// ...

Add `app.UseCors()` in `Program.cs` before `app.UseAuthorization()`. Middleware runs in the order it is added, so placement matters for authorization and endpoints. section 3.1.1

The default policy can allow origins specified by `AllowedOrigins`. Although `app.UseCors("AnyOrigin")` would apply the named policy globally, reserve an all-origins policy for cases that need it; endpoint routing or `[EnableCors]` can target particular endpoints instead. If credentials such as cookies or authorization headers are allowed, the origin cannot be `*`: both client and server must acknowledge credentialed requests and specify an origin. section 3.1.1

How Building Web APIs with ASP.NET Core covers it

Cover of Building Web APIs with ASP.NET Core

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Also explained in

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ASP.NET Core in Action, 3eCorsMiddleware is the ASP.NET Core middleware component that evaluates endpoint CORS metadata and applies the corresponding CORS policy.

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Related concepts

UseCorsused by · UseCors is an ASP.NET Core application-builder method that adds CORS middleware and optionally selects a default policy.
cachingconfigures · Caching is the practice of storing reusable data or computation results so later access can avoid repeating retrieval or computation.
CORSuses · Cross-Origin Resource Sharing (CORS) is a web standard that uses HTTP headers to let servers specify which origins may access their resources through browsers.
middlewarekind of · Middleware is an intermediate software component or layer that processes or mediates requests, messages, or operations between other components, often adding behavior or controlling their flow.

This explainer was generated by Manning's knowledge graph from the text of Building Web APIs with ASP.NET Core. The section links point to the parts of the book it draws on.