How can I pass a value from an ASPX page to another in a different domain

I have an ASPX page in my Application. ASPX pages from other applications in different domain can call this page. But how do I return a value to the calling ASPX page in a different application?

How an ASPX page can return 开发者_开发问答a value to calling page in a different app?

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The cleanest solution is to use a web service (here's an older introductory article). Failing that, the calling pages will likely have to be able to parse or scrape the content of your page in order to retrieve a return value.