Generate route with one parameter replaced

Question

I have created a website where localization is being done by the first parameter in my route. So each URL looks like /{lang}/... with lang being nl, en, fr, ....

In my header, I would like to add a language picker that redirects to the current page in the selected language. I have used the code below and it worked perfectly.

<a asp-route-lang="@lang.Code.ToString()">
    @lang.Name
</a>

However, when the current route contains other route parameters, these are all gone for the generated URL. Is there any way to tell the route generator to keep all other existing route parameters for the new URL?

I have different route definitions with different parameters, so there is no possibility to add them to the generated URL manually.

Answer 1

The answer of NightOwl888 gave me the idea on how to solve this.

I take the RouteData from the current context and use this as the base for the route generator. In my foreach loop, I overwrite the lang parameter with the one that I need.

Now I can use the Url.Action() function with this data to generate the correct URL.

@{
    var routeValues = this.ViewContext.RouteData.Values;
    var controller = routeValues["controller"] as string;
    var action = routeValues["action"] as string;
}

@foreach (var lang in Model.SiteLanguages)
{
    routeValues["lang"] = lang.Code.ToString();

    <a href="@Url.Action(action, controller, routeValues)">
        @lang.Name.UcFirst()
    </a>
}