Architecture Overview

WebApiClientCore is a declarative HTTP client framework for .NET that allows you to define HTTP requests through interfaces and attributes, eliminating the need to manually construct HttpRequestMessage.

Core Design Philosophy

Declarative Programming

Traditional HTTP client code:

// Traditional approach
public async Task<User> GetUserAsync(string id)
{
    var client = _httpClientFactory.CreateClient();
    var response = await client.GetAsync($"http://api.example.com/users/{id}");
    response.EnsureSuccessStatusCode();
    var json = await response.Content.ReadAsStringAsync();
    return JsonSerializer.Deserialize<User>(json);
}

Using WebApiClientCore:

// Declarative
public interface IUserApi
{
    [HttpGet("users/{id}")]
    Task<User> GetAsync(string id);
}

Core Concepts

Core Components

1. Attribute System

Attribute Category	Description	Examples
HTTP Methods	Define request method and path	[HttpGet], [HttpPost]
Content Attributes	Define request body format	[JsonContent], [FormContent]
Return Attributes	Define response parsing method	[JsonReturn], [XmlReturn]
Filters	Request/response interception	[LoggingFilter], [Timeout]
Host Attributes	Define base URL	[HttpHost]

2. IApiParameter

Self-describing parameter types that allow parameters to control their own serialization and transmission:

public class FaceModel : IApiParameter
{
    public Bitmap Image { get; set; }
    
    public Task OnRequestAsync(ApiParameterContext context)
    {
        // Custom serialization logic
    }
}

3. IApiFilter

Filters for request and response interception:

public class SignFilter : IApiFilter
{
    public Task OnRequestAsync(ApiRequestContext context)
    {
        // Before request: Add signature
    }
    
    public Task OnResponseAsync(ApiResponseContext context)
    {
        // After response: Log
    }
}

4. ITask<T>

Asynchronous tasks with conditional retry support:

public interface IUserApi
{
    [HttpGet("users/{id}")]
    ITask<User> GetAsync(string id);
}

var user = await userApi.GetAsync(id)
    .Retry(3)
    .WhenCatch<HttpRequestException>();

Request Processing Flow

Dependency Injection

WebApiClientCore integrates deeply with ASP.NET Core's dependency injection system:

// Register interface
services.AddHttpApi<IUserApi>()
    .ConfigureHttpApi(o =>
    {
        o.HttpHost = new Uri("http://api.example.com/");
    })
    .ConfigureHttpClient(c =>
    {
        c.Timeout = TimeSpan.FromSeconds(30);
    });

// Usage
public class UserService
{
    private readonly IUserApi _userApi;
    
    public UserService(IUserApi userApi)
    {
        _userApi = userApi;
    }
}

Extension Packages

Package Name	Function
WebApiClientCore	Core package
WebApiClientCore.Extensions.OAuths	OAuth2 and token management
WebApiClientCore.Extensions.NewtonsoftJson	Newtonsoft.Json support
WebApiClientCore.Extensions.JsonRpc	JSON-RPC protocol support
WebApiClientCore.OpenApi.SourceGenerator	OpenAPI code generation tool

Comparison with Other Solutions

Feature	WebApiClientCore	Refit	HttpClient
Declarative Interface	✅	✅	❌
Compile-time Checking	✅	✅	❌
Conditional Retry	✅ ITask	❌	❌
Custom Parameter Serialization	✅ IApiParameter	❌	✅
OAuth Extension	✅	Manual implementation	Manual implementation
AOT Support	✅	❌	✅

Next Steps

• Getting Started
• HTTP Attributes
• Content Attributes
• Exception Handling