Remove a query string from the request before processing it

Question

I would like to remove a particular query string (namely fbclid), which Facebook adds to shared links for tracking (I assume). I need to do this for all of my routes to work, but I couldn't find a straightforward solution.

I'm using ASP.NET Core 2.0, AWS lambda, API gateway.

I've tried to use a rewriter, but it throws an exception when the replacement is an empty string. Here is my code:

app.UseRewriter(new RewriteOptions()
    .AddRewrite("\\?fbclid=(\\w*)", string.Empty, false));

I do not wish to redirect to a clean URL or get the URL without the query param. Rather, I need to change the current request for the rest of the pipeline to process it correctly.

Answer 1

For removing the query string, you could try Middleware like

app.Use(async (context,next) =>
{                
    if (context.Request.Query.TryGetValue("fbclid", out StringValues query))
    {
        var items = context.Request.Query.SelectMany(x => x.Value, (col, value) => new KeyValuePair<string, string>(col.Key, value)).ToList();
        // At this point you can remove items if you want
        items.RemoveAll(x => x.Key == "fbclid"); // Remove all values for key
        var qb = new QueryBuilder(items);
        context.Request.QueryString = qb.ToQueryString();
    }
    await next.Invoke();
});