Question

I’m implementing a custom control and in this control I need to write a bunch of links to the current page, each one with a different query parameter. I need to keep existing query string intact, and add (or modify the value of ) an extra query item (eg. ‘page’):

'Default.aspx?page=1' 'Default.aspx?page=2' 'Default.aspx?someother=true&page=2' 

etc.

Is there a simple helper method that I can use in the Render method … uhmm … like:

Page.ClientScript.SomeURLBuilderMethodHere(this,'page','1'); Page.ClientScript.SomeURLBuilderMethodHere(this,'page','2'); 

That will take care of generating a correct URL, maintain existing query string items and not create duplicates eg. page=1&page=2&page=3?

Rolling up my own seems like such an unappealing task.

Answer 1

I’m afraid I don’t know of any built-in method for this, we use this method that takes the querystring and sets parameters

    /// <summary>     /// Set a parameter value in a query string. If the parameter is not found in the passed in query string,     /// it is added to the end of the query string     /// </summary>     /// <param name='queryString'>The query string that is to be manipulated</param>     /// <param name='paramName'>The name of the parameter</param>     /// <param name='paramValue'>The value that the parameter is to be set to</param>     /// <returns>The query string with the parameter set to the new value.</returns>     public static string SetParameter(string queryString, string paramName, object paramValue)     {         //create the regex         //match paramname=*         //string regex = String.Format(@'{0}=[^&]*', paramName);         string regex = @'([&?]{0,1})' + String.Format(@'({0}=[^&]*)', paramName);          RegexOptions options = RegexOptions.RightToLeft;         // Querystring has parameters...         if (Regex.IsMatch(queryString, regex, options))         {             queryString = Regex.Replace(queryString, regex, String.Format('$1{0}={1}', paramName, paramValue));         }         else         {             // If no querystring just return the Parameter Key/Value             if (queryString == String.Empty)             {                 return String.Format('{0}={1}', paramName, paramValue);             }             else             {                 // Append the new parameter key/value to the end of querystring                 queryString = String.Format('{0}&{1}={2}', queryString, paramName, paramValue);             }         }         return queryString;     } 

Obviously you could use the QueryString NameValueCollection property of the URI object to make looking up the values easier, but we wanted to be able to parse any querystring.