How to build a query string for a URL in C#?

Question

A common task when calling web resources from a code is building a query string to including all the necessary parameters. While by all means no rocket science, there are so

Answer 1

    public static string ToQueryString(this Dictionary source)
    {
        return String.Join("&", source.Select(kvp => String.Format("{0}={1}", HttpUtility.UrlEncode(kvp.Key), HttpUtility.UrlEncode(kvp.Value))).ToArray());
    }

    public static string ToQueryString(this NameValueCollection source)
    {
        return String.Join("&", source.Cast().Select(key => String.Format("{0}={1}", HttpUtility.UrlEncode(key), HttpUtility.UrlEncode(source[key]))).ToArray());
    }