DNV.Context.HttpClient

The DNV.Context.HttpClient package is a .Net library which provides extension methods for adding context data in http client request.

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Basic example

Add Context to Http Client Context Handler

First define the context payload, ex

public class Identity
{
    public string? Name { get; set; }
    public string? Country { get; set; }
    public string? City { get; set; }
}

When application startup, call an extension method AddHttpClientContext. This will add a Http message handler(HttpClientContextHandler) to the named http client. HttpClientContextHandler will serialize context data to request headers before send http request.

In this example, it adds an empty Identity object to HttpClientContextHandler.

builder.Services.AddAspNetContext((context) => (true, new Identity()), null);

Send Http Request With Context Data

In your controller, initialize context first, then send request with context data.

public class HomeController : Controller
{
    private readonly IHttpClientFactory _httpClientFactory;
    private readonly IContextCreator<Identity> _contextCreator;

    public HomeController(IHttpClientFactory httpClientFactory,
                            IContextCreator<Identity> contextCreator)
    {
        _httpClientFactory = httpClientFactory;
        _contextCreator = contextCreator;
    }       

    [HttpPost]
    [Route("useridentity")]
    public async Task<IActionResult> UserIdentity([FromForm] Identity userIdentity)
    {
        // Initialize context
        _contextCreator.InitializeContext(new Identity
        {
            Name = userIdentity.Name,
            Country = userIdentity.Country,
            City = userIdentity.City
        }, Guid.NewGuid().ToString());

        // Call extension method to create http client
        var client = _httpClientFactory.CreateContextClient<Identity>();
        client.BaseAddress = new Uri("https://localhost:7174");

        // Send request
        var request = new HttpRequestMessage(HttpMethod.Get, new Uri("api/identity/user", UriKind.Relative));
        var resp = await client.SendAsync(request);
        ......
    }
}

In your api controller, get context from http request header, and returns to caller.

[HttpGet]
[Route("user")]
public Identity GetUser()
{            
    var headers = _httpContext?.Request.Headers[AspNetContextAccessor<Identity>.HeaderKey];
    if(headers.HasValue)
    {                
        var testContext = JsonSerializer.Deserialize<TestContext>(headers.Value.ToString(), new JsonSerializerOptions
        {
            PropertyNameCaseInsensitive = true,
        });
        return testContext?.Payload!;
    }
    return new Identity();
}

Display Context Data in Page

[HttpPost]
[Route("useridentity")]
public async Task<IActionResult> UserIdentity([FromForm] Identity userIdentity)
{
    ......
    
    // Receive data and returns to the view for display.
    var content = resp.Content.ReadAsStringAsync();
    var identity = JsonSerializer.Deserialize<Identity>(content.Result, new JsonSerializerOptions
    {
        PropertyNameCaseInsensitive = true
    });

    ViewData["Name"] = identity?.Name;
    ViewData["Country"] = identity?.Country;
    ViewData["City"] = identity?.City;
    return View("Result");
}