How to send custom headers from mvc project to a web api project?

Question

I have two applications running together at the same time. In my mvc project I have a middleware that will use TempData in order to pass the values of username and ipAddress and add it to the response headers. What I am trying to do is with those headers that are added in the middleware of the mvc project is to pass those headers over to the web api project so I can be able to use the username and ipaddress and have the same correlationid. How can I send/forward those custom headers that are in the mvc project over to the web api project?

Middleware in mvc project:

public class CorrelationIdMiddleware
{
    private readonly RequestDelegate _next;
    private readonly ILogger _logger;
    private readonly ITempDataDictionaryFactory _tempDataDictionaryFactory;
    public CorrelationIdMiddleware(RequestDelegate next, ILoggerFactory loggerFactory, ITempDataDictionaryFactory tempDataDictionaryFactory)
    {
        _next = next;
        _logger = loggerFactory.CreateLogger<CorrelationIdMiddleware>();
        _tempDataDictionaryFactory = tempDataDictionaryFactory;
    }

    public async Task Invoke(HttpContext context)
    {
        string correlationId = null;
        string userName;
        string ipAddress;

        var tempData = _tempDataDictionaryFactory.GetTempData(context);

        var key = context.Request.Headers.Keys.FirstOrDefault(n => n.ToLower().Equals("x-correlation-id"));
        if (!string.IsNullOrWhiteSpace(key))
        {
            correlationId = context.Request.Headers[key];
            _logger.LogInformation("Header contained CorrelationId: {@CorrelationId}", correlationId);
        }
        else
        {
            if (tempData.ContainsKey("username") && tempData.ContainsKey("ipaddress"))
            {
                userName = tempData.Peek("username").ToString();
            
                ipAddress = tempData.Peek("ipaddress").ToString();

                context.Response.Headers.Append("X-username", userName);
                context.Response.Headers.Append("X-ipAddress", ipAddress);
            }

            correlationId = Guid.NewGuid().ToString();
            _logger.LogInformation("Generated new CorrelationId: {@CorrelationId}", correlationId);
        }
        context.Response.Headers.Append("x-correlation-id", correlationId);
        using (LogContext.PushProperty("CorrelationId", correlationId))
        {
            await _next.Invoke(context);
        }
    }
}

now moving to my web api project:

At first I had the same exact code for my mvc middleware but it never entered the if statement for the tempdata.containkey so I removed tempdata implementation.

public class CorrelationIdMiddleware
{
    private readonly RequestDelegate _next;
    private readonly ILogger _logger;
    public CorrelationIdMiddleware(RequestDelegate next, ILoggerFactory loggerFactory)
    {
        _next = next;
        _logger = loggerFactory.CreateLogger<CorrelationIdMiddleware>();
    }

    public async Task Invoke(HttpContext context)
    {
        string correlationId = null;

        var key = context.Request.Headers.Keys.FirstOrDefault(n => n.ToLower().Equals("x-correlation-id"));
        if (!string.IsNullOrWhiteSpace(key))
        {
            correlationId = context.Request.Headers[key];
            _logger.LogInformation("Header contained CorrelationId: {@CorrelationId}", correlationId);
        }
        else
        {
            correlationId = Guid.NewGuid().ToString();
            _logger.LogInformation("Generated new CorrelationId: {@CorrelationId}", correlationId);
        }
        context.Response.Headers.Append("x-correlation-id", correlationId);
        using (LogContext.PushProperty("CorrelationId", correlationId))
        {
            await _next.Invoke(context);
        }
    }
}

Answer 1

Your HttpClient call works independently of your controllers and middleware.

You need to add the headers to the HttpClient before making the API call. To do this you'll need the home controller to store the headers, or somehow pass the headers back to the home controller, then pass them into the HttpClient logic