ASP.NET的Cookie跨域问题
将Cookie的有效范围限制到域。?
默认情况下，Cookie 与特定的域相关联。
例如，如果您的站点是 ? www.contoso.com，那么当用户向该站点请求页面时，
您编写的Cookie就被发送到服务器。（有特定路径值的Cookie除外） ?
如果您的站点有子域（例如 ? contoso.com、sales.contoso.com ? 和 ? support.contoso.com），
就可以把Cookie同特定的子域相关联。为此，需要设置Cookie的 ? Domain ? 属性，如下所示：?

总的写法:
Response.Cookies("MyCookie").Domain = "cnblogs.com";
Response.Cookies("MyCookie").Path = "/"
Response.Cookies("MyCookie").Expires = Now + 365;
Response.Cookies("MyCookie")("Test") = "test";

.NET 清除Cookie
HttpCookie cookie = System.Web.HttpContext.Current.Request.Cookies[cookiename];
if (cookie != null)
{
??????????????? cookie.Values.Clear();
??????????????? SetUserCookieExpireTime(cookiename, -1);
??????????????? cookie.Domain = _domain;
??????????????? System.Web.HttpContext.Current.Response.Cookies.Set(cookie);
}
public static void SetUserCookieExpireTime(string key, int days)
{
??????????? System.Web.HttpContext.Current.Response.Cookies[key].Domain = _domain;
??????????? System.Web.HttpContext.Current.Response.Cookies[key].Path = _cookiepath;
??????????? System.Web.HttpContext.Current.Response.Cookies[key].Expires = DateTime.Now.AddDays(days);
}
.NET 添加/更新Cookie
public static void AddUserCookies(string key,string value, string cookiename, string domain)
{
??????????? HttpCookie cookie = System.Web.HttpContext.Current.Request.Cookies[cookiename];
??????????? if (cookie == null)
??????????? {
??????????????? cookie = new HttpCookie(cookiename);
??????????????? cookie.Domain = domain;
??????????????? cookie.Path = _cookiepath;

??????????????? cookie.Values.Add(key, value);
??????????????? HttpContext.Current.Response.AppendCookie(cookie);
??????????? }
??????????? else
??????????? {
??????????????? if (System.Web.HttpContext.Current.Request.Cookies[cookiename].Values[key] != null)
??????????????? {
??????????????????? cookie.Values.Set(key, value);
??????????????? }
??????????????? else
??????????????? {
??????????????????? cookie.Domain = domain;
??????????????????? cookie.Path = _cookiepath;

??????????????????? cookie.Values.Add(key, value);
??????????????????? HttpContext.Current.Response.AppendCookie(cookie);
??????????????? }
??????????? }
}

这种写法实现cookie跨域跨目录