Reading Request Headers Across Multiple .NET Core API Controllers

I was working on creating a .NET Core-based API and came across a requirement to read a particular request header across the API controllers.  To understand it better, let us say there are two API controllers,

1.    InvoiceController 2.    ProductController

We need to read the value of a particular Request Header in both controllers.
 
To do that, add a middleware class; I am naming it RequestCodeMiddleware, as we will read a request header named-  “Request-Code.”

public class RequestCodeMiddleware
{
    private readonly RequestDelegate _next;
 
    public RequestCodeMiddleware(RequestDelegate next)
    {
        _next = next;
    }
 
    public async Task Invoke(HttpContext context)
    {
        // Read the request code here. This is just an example, replace it with your actual logic.
        var requestCode = context.Request.Headers["Request-Code"].FirstOrDefault();
        // Add the request code to the HttpContext
        context.Items["RequestCode"] = requestCode+"middle ware";
        // Call the next middleware in the pipeline
        await _next(context);
    }
}

After creating the middleware class, register it to the API handling pipeline by adding the below code,

if (app.Environment.IsDevelopment())
{
    
     app.UseSwagger();
    
app.UseSwaggerUI();

}

app.UseMiddleware<RequestCodeMiddleware>();
app.UseHttpsRedirection();

app.MapControllers();

app.Run();

Now, you can read the request header in a ProductController’s GET Action, as shown below.

public class product : ControllerBase
{
   
    [HttpGet]
    public string Get()
    {
        var requestCode = HttpContext.Items["RequestCode"] as string;
        return requestCode;
    }
}

So far, so good; however, there is still a challenge: the above code must be duplicated to read the request header in the multiple Actions. To avoid that, we can read it inside the controller’s constructor; however, HttpContext is unavailable inside a controller’s constructor.
 
Another approach is to use IHttpContextAccesor.
 
To use IHttpContextAccesor, register it in the API startup pipeline as shown below,

builder.Services.AddHttpContextAccessor();

Now, in the InvoiceController's constructor, you can inject IHttpContextAccesor to read the request header, as shown in the code listing below.

public class invoice : ControllerBase
    {
 
        private readonly IHttpContextAccessor _httpContextAccessor;
        private string _requestCode;
 
        public invoice(IHttpContextAccessor httpContextAccessor)
        {
            _httpContextAccessor = httpContextAccessor;
            _requestCode = _httpContextAccessor.HttpContext.Items["RequestCode"] as string;
        }
 
     // Your action methods..
     // GET: api/<invoice>
        [HttpGet]
        public string Get()
        {
            return _requestCode;
        }
      }

In this way, we can read a request header in multiple controllers.  I hope you find this post helpful. Thanks for reading.