Change Single URL query string value

Question

I have an ASP.NET page which takes a number of parameters in the query string:

search.aspx?q=123&source=WebSearch

This would display th

Answer 1

This is pretty arbitrary, in .NET Core at least. And it all boils down to asp-all-route-data

Consider the following trivial example (taken from the "paginator" view model I use in virtually every project):

public class SomeViewModel 
{

    public Dictionary NextPageLink(IQueryCollection query)
    {
        /*
         * NOTE: how you derive the "2" is fully up to you
         */
        return ParseQueryCollection(query, "page", "2");
    }

    Dictionary ParseQueryCollection(IQueryCollection query, string replacementKey, string replacementValue)
    {
        var dict = new Dictionary()
        {
            { replacementKey, replacementValue }
        };

        foreach (var q in query)
        {
            if (!string.Equals(q.Key, replacementKey, StringComparison.OrdinalIgnoreCase))
            {
                dict.Add(q.Key, q.Value);
            }
        }

        return dict;
    }
}

Then to use in your view, simply pass the method the current request query collection from Context.Request:

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