C# ASP.NET MVC RestAPI: Process headers before body and and parameters are received

Question

Usually in network protocols, header of request are preprocessed and then body of request will be processed afterwards. In case of HTTP I'm not sure but I want to know are there any methods to process header before body of request and its parameters?

Talking in C# way, are there any methods to process request header before Controller method gets fired or not?

If answer is yes, I want to send client version to my server and In case they are not matching sending client suitable response. I want to do this since it might happen that body of my request be big (e.g. 10MBs) and I want to preprocess header before waiting to receive whole HTTP request.

Answer 1

The answer is yes, you can use the action filters. https://learn.microsoft.com/en-us/aspnet/core/mvc/controllers/filters?view=aspnetcore-3.1#action-filters

public class MySampleActionFilter : IActionFilter
{
    public void OnActionExecuting (ActionExecutingContext context)
    {
        // Do something before the action executes.
    }

    public void OnActionExecuted(ActionExecutedContext context)
    {
        // Do something after the action executes.
    }
}

As per documentation you can override the action context and short circuit the result, without going into the controller.

Result - setting Result short-circuits execution of the action method and subsequent action filters.

You can find your headers like this

var headers = context.HttpContext.Request.Headers;

// Ensure that all of your properties are present in the current Request
if(!String.IsNullOrEmpty(headers["version"])
{
     // All of those properties are available, handle accordingly

     // You can redirect your user based on the following line of code
     context.Result = new RedirectResult(url);
}
else
{
     // Those properties were not present in the header, redirect somewhere else
}