DelegatingHandler
DelegatingHandler is a .NET HttpMessageHandler base class that forwards requests and responses to an inner handler while permitting additional processing.
.NET MAUI in Action
A delegating handler is an HTTP message handler that can inspect or modify a request or response before passing it to another handler.
- How it is used
- Automates authenticated HTTP requests by attaching access-token headers through an HttpClient handler pipeline.
- How deep it goes
- Explains inheritance, SendAsync, request modification, dependency-injection registration, named clients, and handler chaining.
- Examples
- Demonstrates MauiStockTake's AuthHandler, AuthService login flow, named authenticated client, and chained request handlers.
- What you can do after
- Configure an HttpClient that automatically adds authentication headers and composes multiple request policies.
ASP.NET Core in Action, 3e
DelegatingHandler is a .NET HttpMessageHandler base class that forwards processing to an inner handler while allowing additional behavior.
- How it is used
- Applies cross-cutting behavior such as authentication, logging, and metrics to requests made through named or typed clients.
- How deep it goes
- Explains derivation, SendAsync, dependency-injection registration, pipeline ordering, and request-response flow.
- Examples
- Demonstrates an API-key handler and its registration alongside transient error handling for ExchangeRatesClient.
- What you can do after
- Build custom request behavior, register it with dependency injection, and apply it to selected HttpClient pipelines.
Read how ASP.NET Core in Action, 3e explains DelegatingHandler →
Related concepts
- AddHttpMessageHandlerused by · AddHttpMessageHandler is an IHttpClientBuilder extension method that adds a delegating handler type to an HttpClient handler pipeline.
- custom HttpMessageHandlerincludes · A custom HttpMessageHandler is an application-defined HTTP pipeline component that modifies or observes requests and responses.
- HttpMessageHandlerkind of · HttpMessageHandler is an abstract .NET component that processes HTTP request and response messages within an HttpClient handler chain.
- HTTP clientuses · An HTTP client is software or an API component that sends HTTP requests and receives and processes HTTP responses.
- single responsibility principleimplements · The single responsibility principle is a software design principle that gives a component one focused responsibility and one primary reason to change.
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