public static class MyExtensions {
      public static void AppendQueryArgs(this UriBuilder builder, IEnumerable<KeyValuePair<string, string>> args)
		{
			var keyValuePairs = args as KeyValuePair<string, string>[] 
				?? args.ToArray();
			if (args == null || !keyValuePairs.Any()) 
				return;
			var sb = new StringBuilder(50 + (keyValuePairs.Count() * 10));
			if (!String.IsNullOrEmpty(builder.Query))
			{
				sb.Append(builder.Query.Substring(1));
				sb.Append('&');
			}
			sb.Append(CreateQueryString(keyValuePairs));

			builder.Query = sb.ToString();
		}
}

			var builder = new UriBuilder(HttpContext.Current.Request.PhysicalApplicationPath);

			builder.AppendQueryArgs(
				new Dictionary<string, string> {
					{ "Limit", 40},
					{ "Other", "my value" }
				});

			Response.Redirect(builder.Uri);

	...
	public ActionResult MyAction()
	{
		...
		return RedirectToAction("ActionName", new {Limit = 20, Other = "другие значения" });
	}
	...