Adding or Replacing a Page item in a QueryString in C#.

Question

Can this code be improved? I'm avoiding using the QueryString collection because the query string may contain eg: OrderBy=Column1&OrderBy=Column2 and it didn't seem helpful to start with those switched into QueryString["OrderBy"]=="Column1,Column2";

 var query = "";
 if (urlHelper.RequestContext.HttpContext.Request.Url != null)
 {
 query = urlHelper.RequestContext.HttpContext.Request.Url.Query.TrimStart('?');
 if (query.Length > 0)
 {
 var kvp =
 query.Split('&').Select(x => x.Split('='))
 .Select(x => new { Key = x[0], Value = (x.Length > 0) ? x[1] : ""})
 .Where(x => x.Key != "page")
 .ToList();
 kvp.Add(new { Key = "page", Value = number.ToString() });
 query = String.Join("&", kvp.Select(x => x.Key + "=" + x.Value).ToArray());
 }
 else query = String.Format("page={0}", number);
 }

• Snowbear: Why do you think it won't be helpful to switch to QueryString["OrderBy"]=="Column1,Column2". It seems to be more regular structure than several parameters with the same name.
• mootinator: The original query string comes from form data. MVC binds the multiple "OrderBy" as an IEnumerable<string>. If I convert the QueryString collection into a RouteValuesDictionary to recycle the query string the IEnumerable only has one value, and it breaks the view as a result. I guess it would be a valid suggestion to have the controller handle both cases gracefully.

Answer 1

I think that yes this code can be improved.

use a regular expression:

 var newQuery = Regex.Replace(currentQuery, @"(?i)(page=\d*&?)", "").TrimEnd('&');
 if (newQuery.Length > 0)
 newQuery += string.Format("&Page={0}", currentPageNo);
 else
 newQuery = string.Format("Page={0}", currentPageNo);