How to get the QueryString from an ashx file?

There is an ashx file containing "ProcessRequest(Http开发者_JAVA技巧Context context)" method which gets triggered automatically. When and how does it get fired? Another question, How can I get the current QueryString when I am inside this file? When I type "context.Request.QueryString" it says it's null or empty although the address have arguments.

---

The ProcessRequest method is called when a request for the ashx file is made. The http context object is passed in to enable access to the stuff like the querystring, headers, etc.

Re: querystring access:

The following will work as long as "ID" is passed on the querystring.

http://example.com/MyHandler.ashx?ID=12345

public void ProcessRequest (HttpContext context) 
{
    string ID = context.Request.QueryString["ID"];
}