ASP.NET - How to share cookie value across domain

In one domain, I coded like below.

var cookie = new HttpCookie("cookieName", "userName");
Response.SetCookie(cookie);
return Redirect("http://www.something.com/");

In another(www.somthing.com) domain,

if (Request != null && Request.Cookies.Count > 0)
            {
                string name = Request.Cookies["cookieName"] != null ? Request.Cookies["cookieName"].Value : null;
            }

but its not working, value always empty.

I cannot use query string. I have to use only cookie.

Please give me a solution.

You need to read this to better understand the limitations of accessing cookie information across domains:

http://www.codeproject.com/Tips/610537/Browser-Cross-Domain-Explained

Thanks dude.