Append QueryString to href in asp.net core Anchor Helper Tag

Question

I am trying to add anything in the query of the request to anchors in the html result:

Fictitious example:

User makes a request (note that band and song coul

Answer 1

There doesn't seem to be any official way to do this yet.

If the @Context.GetRouteData().Values works you should use it instead. The idea behind it is, that GetRouteData gets the current route information from the routing middleware as key value pairs (Dictionary) which should also contain query parameters.

I am not sure if it works in your case and if asp-route-band & asp-route-song are hard-coded or taken from route in your case.

In case that may not work, you could try the following extension method & class:

public static class QueryParamsExtensions
{
    public static QueryParameters GetQueryParameters(this HttpContext context)
    {
        var dictionary = context.Request.Query.ToDictionary(d => d.Key, d => d.Value.ToString());
        return new QueryParameters(dictionary);
    }
}

public class QueryParameters : Dictionary<string, string>
{
    public QueryParameters() : base() { }
    public QueryParameters(int capacity) : base(capacity) { }
    public QueryParameters(IDictionary<string, string> dictionary) : base(dictionary) { }

    public QueryParameters WithRoute(string routeParam, string routeValue)
    {
        this[routeParam] = routeValue;

        return this;
    }
}

It basically abstracts your code from above behind a extension method and returns a QueryParameters type (which is an extended Dictionary<string,string>) with a single additional method for pure convenience, so you can chain multiple .WithRoute calls, since Add method of dictionary has a void return type.

You'd be calling it from your View like this

<a  asp-controller="topic"
    asp-action="topic" 
    asp-all-route-data="@Context.GetQueryParameters().WithRoute("band", "iron-maiden").WithRoute("song", "run-to-the-hills");"
>
    Iron Maiden - Run to the hills
</a>