Migrating to core, but stuck with old "Module" (HttpApplication) - asp.net-core

Question

I've done some parts for the Middleware in startup etc..
So this is my class
public class AcceptQueryMiddleware
{
private const string Realm = "Basic realm=My Sales System";
private readonly RequestDelegate _next;
private static readonly IDictionary<Regex, string> FormatAcceptMap = new Dictionary<Regex, string>();
public AcceptQueryMiddleware(RequestDelegate next)
{
_next = next;
}
public void AcceptQueryHttpModule()
{
RegisterFormatAcceptQuery("csv", "text/csv");
RegisterFormatAcceptQuery("excel", "application/vnd.ms-excel");
RegisterFormatAcceptQuery("nav", "application/navision");
}
private static void RegisterFormatAcceptQuery(string format, string acceptHeader)
{
var regex = new Regex(#"([?]|[&])format=" + format);
FormatAcceptMap.Add(regex, acceptHeader);
}
private static void OnApplicationBeginRequest(object sender, EventArgs eventArgs)
{
var app = sender as HttpApplication;
if (app == null) { return; }
var url = app.Request.RawUrl;
foreach (var format in FormatAcceptMap)
{
if (format.Key.Match(url).Success)
{
app.Request.Headers["Accept"] = format.Value;
break;
}
}
}
public void Dispose()
{
}
}
How do I convert it to Core? Way around it?
Specifically the HttpApplication that is not supported in .NET Core..
Or do you have any links or tips I can follow?

Answer 1

You want to migrate your HTTP module to a middleware. See the documentation to learn how.
In your case, you're using the HttpApplication to access request-related data. You're getting the raw URL and adding some headers. That's something you can easily do in a middleware. Here's an example:
public class AcceptQueryMiddleware
{
private readonly RequestDelegate _next;
public AcceptQueryMiddleware(RequestDelegate next)
{
_next = next;
}
public async Task Invoke(HttpContext context)
{
// Do your "before" stuff here (use the HttpContext)
await _next.Invoke(context);
// Do your "after" stuff here
}
}
and call app.UseMiddleware<AcceptQueryMiddleware>(); in your Startup class (in the Configure method).