HTTP Client Attributes¶

Attributes define the shape of your HTTP client — which class is a client, which methods map to endpoints, and how parameters are bound.

Class-Level¶

`[HttpClient]` / `[HttpClient<TConfig>]`¶

Marks a partial class as an HTTP client. The optional generic parameter binds a configuration type for base address and settings.

Property	Type	Default	Description
`BaseAddress`	`string?`	`null`	Base URL for all requests. Can also be set via configuration.
`JsonContext`	`Type?`	`null`	Optional `JsonSerializerContext` type for STJ source-generated serialization.

// Without configuration binding
[HttpClient(BaseAddress = "https://api.example.com")]
public partial class SimpleClient;

// With configuration binding
[HttpClient<GitHubApiConfig>]
public partial class GitHubClient;

Configuration binding

When using [HttpClient<TConfig>], the base address and other settings are resolved from the bound configuration provider at runtime.

Method-Level (HTTP Verbs)¶

Each HTTP verb attribute marks a partial method as an API endpoint.

Attribute	HTTP Method
`[Get(path)]`	`GET`
`[Post(path)]`	`POST`
`[Put(path)]`	`PUT`
`[Patch(path)]`	`PATCH`
`[Delete(path)]`	`DELETE`

The path parameter is required and supports {param} templates that bind to method parameters:

[Get("/users/{userId}/orders/{orderId}")]
private partial Order GetOrder(int userId, string orderId);

Return types

Methods must return Task<T> where T is the response type (e.g., Task<User>). Use Task<Unit> for endpoints with no response body.

Parameter-Level¶

Attribute	Description	Example
`[Path]`	Path parameter — auto-detected from `{param}` templates	`int id` in `/users/{id}`
`[Query]`	Query string parameter. Optional `Name` for override.	`[Query("per_page")] int perPage`
`[Header(name)]`	Adds an HTTP header to the request	`[Header("X-Api-Version")] string version`
`[Body]`	Request body, serialized as JSON	`[Body] CreateUserRequest request`
`[Form]`	Form-urlencoded field. Optional `Name` for override.	`[Form("To")] string to`

Path parameter auto-detection

Parameters matching {param} placeholders in the path are automatically treated as path parameters — the [Path] attribute is only needed when the parameter name differs from the template placeholder.

[Form] and [Body] are mutually exclusive

A method cannot have both [Form] and [Body] parameters. [Body] sends a JSON payload (application/json), while [Form] sends form-urlencoded fields (application/x-www-form-urlencoded). The analyzer reports DSHTTP05 if both are used on the same method.

Form-Encoded Requests¶

Use [Form] parameters for APIs that accept application/x-www-form-urlencoded content (e.g., Twilio, OAuth token endpoints):

[Post("/2010-04-01/Accounts/{accountSid}/Messages.json")]
public partial Task<SmsResponse> SendSms(
    string accountSid,
    [Form("To")] string to,
    [Form("From")] string from,
    [Form("Body")] string body);

When the Name is omitted, the parameter name is used as the form field name:

[Post("/oauth/token")]
public partial Task<TokenResponse> GetToken(
    [Form] string grant_type,
    [Form] string client_id,
    [Form] string client_secret);

Authentication¶

Authentication attributes configure how credentials are attached to requests. See the Authentication page for full details.

Attribute	Description
`[BearerAuth]`	Bearer token from configuration
`[ApiKeyAuth]`	API key in a named header
`[BasicAuth]`	Basic username/password credentials