Web Forms :: Set Cookie In Response Not Coming Back Through Request

My web site is integrated into a client web site. Client web site reaches out to my site through an Xml request and I return Html embedded in an Xml response. Client site then displays the Html in an area on a page on their site. All is well so far...

Now, there is a link on the Html that does an HttpPost back to my site which causes a re-direct to another page on my site. i.e. [URL] -> HttpPost -> [URL]-> Response.Redirect("CookieTest.aspx"). Still, all is well. [URL]

All of the above can occur without authentication to mysite. Where I start running into problems is when CookieTest wants to do a FormsAuthentication.SetAuthCookie(). If I put a button on CookieTest that does FormsAuthentication.SetAuthCookie() and then Response.Redirect("SecurePage.aspx"), still under [URL], the SecurePage does not recognize the authentication because the auth cookie is not present.

1. Navigate straight to CookieTest.aspx

So I simplfied the problem into basic cookie set/read excercise and used the code below to test out cookie writing/reading ability. When I call the page directly from the browser I see that on initial load the response cookies are empty. Then on button click I see that the cookie is properly set in the response. Then on subsequent page refresh I see that the page load shows the request cookie.

2. Navigate to CookieTest.aspx in an HttpPost from [URL], as mentioned above.

Now on button click I see the cookie in the Response but do not see it come back in the Request of subsequent page refreshes, as if the client browser is rejecting cookies set by my server.

3. Navigate straight to CookieTest.aspx, then do the HttpPost from [URL]

In this case, since the cookie was set during a straight navigation to CookieTest.aspx, the cookie is present in the subsequent HttpPost/Redirect from [URL]. CookieTest.aspx has full access to the cookie and can even delete it.

4. Have CookieTest.aspx pop a new browser window simply sets the cookie and closes itself down.

Similar to #3, if the cookie is set through a popup window and then CookieTest is refreshed the cookie is present in the Request.

Notes:

The code does prove that the client browser accepts cookies.

When my page (CookieTest.aspx) is shown within the frame on the [URl] page, during any link back to my server, the Request.Url.Host shows my domain.

[code]....