URI Routing Rules

All URI routing is handled through the new Uri(Uri baseUri, Uri relativeUri) constructor.

baseUri with Trailing /

• http://a.com/ + b/c/d = http://a.com/b/c/d
• http://a.com/path1/ + b/c/d = http://a.com/path1/b/c/d
• http://a.com/path1/path2/ + b/c/d = http://a.com/path1/path2/b/c/d

baseUri without Trailing /

• http://a.com + b/c/d = http://a.com/b/c/d
• http://a.com/path1 + b/c/d = http://a.com/b/c/d
• http://a.com/path1/path2 + b/c/d = http://a.com/path1/b/c/d

In fact, http://a.com and http://a.com/ are identical—both have a path of /—so they behave the same way.

Best Practices

To avoid routing errors, use the standard baseUri format with a trailing /:

[HttpHost("http://api.example.com/")]  // Recommended: ends with /
public interface IUserApi
{
    [HttpGet("api/users/{id}")]
    Task<User> GetAsync(string id);
}

Dynamic Uri

Using UriAttribute for Absolute Uri Parameter

[LoggingFilter]
public interface IUserApi
{
    [HttpGet]
    ITask<User> GetAsync([Uri] string urlString, [PathQuery] string id);
}

Custom HttpHostBaseAttribute Implementation

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

    [HttpPost("api/users")]
    Task<User> PostAsync([JsonContent] User user);
}

public class ServiceNameHostAttribute : HttpHostBaseAttribute
{
    public string ServiceName { get; }

    public ServiceNameHostAttribute(string serviceName)
    {
        this.ServiceName = serviceName;
    }

    public override Task OnRequestAsync(ApiRequestContext context)
    {
        var hostProvider = context.HttpContext.ServiceProvider.GetRequiredService<HostProvider>();
        string host = hostProvider.ResolveHost(this.ServiceName);
        context.HttpContext.RequestMessage.RequestUri = new Uri(host);
        return Task.CompletedTask;
    }
}