static string AppendQueryStringPairValue(string url, string key, string value)
{
var path = url;
var queryString = string.Empty;
var queryStringPosition = url.IndexOf('?');
if (queryStringPosition > -1)
{
path = url.Substring(0, queryStringPosition);
queryString = url.Substring(queryStringPosition);
}
var querystring = HttpUtility.ParseQueryString(queryString);
querystring.Add(key, value);
var querystringwithAppendedValue = FlattenedQueryString(querystring);
if (!string.IsNullOrEmpty(querystringwithAppendedValue))
{
querystringwithAppendedValue = "?" + querystringwithAppendedValue;
}
return path + querystringwithAppendedValue;
}