C# – Replace item in querystring

asp.netc++query-string

I have a URL that also might have a query string part, the query string might be empty or have multiple items.

I want to replace one of the items in the query string or add it if the item doesn't already exists.

I have an URI object with the complete URL.

My first idea was to use regex and some string magic, that should do it.

But it seems a bit shaky, perhaps the framework has some query string builder class?

I found this was a more elegant solution

var qs = HttpUtility.ParseQueryString(Request.QueryString.ToString());
qs.Set("item", newItemValue);
Console.WriteLine(qs.ToString());

You can use null as the key for the NameValueCollection and it will give you a comma-delimited list of parameter names that don't have values.

For http://example.com?bar=3&foo you would use Request.QueryString[null] and it would retrieve foo.

If you have more than one parameter name without a value, it will give you a value that is comma-delimited.

For http://example.com?bar=3&foo&test you would get foo,test as a value back.

Update:

You can actually use Request.QueryString.GetValues(null) to get the parameter names that don't have values.

Use static ParseQueryString method of System.Web.HttpUtility class that returns NameValueCollection.

Uri myUri = new Uri("http://www.example.com?param1=good&param2=bad");
string param1 = HttpUtility.ParseQueryString(myUri.Query).Get("param1");