Asp.net adding parameter to url string

I'm displaying a list of filtered items in a page, and now I have to limit the displaying by paginating the results.

So if I have url parameters like these:

example.co开发者_如何学运维m/?category=pizza&period=today

where both category and period can also not being showed:

example.com/?period=today

example.com/

how can I add a "Next page" in the end that keeps any previous parameter and adds

&pagenum=5 

or if there are no parameters:

?pagenum=5

Tnx in advance!

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For serverside

string url = Request.Url.GetLeftPart(UriPartial.Path);
url += (Request.QueryString.ToString() == "" ) ? "?pagenum=1" : "?" + Request.QueryString.ToString() + "&pagenum=1";

You can pass in the page number depending on how you are handling this.

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For ASP.Net use the following:

string temp = Request.QueryString["yourParamName"];

Fissh