无法将类型“CustomPrincipal”转换为“System.Security.Principal.IPrincipal”

Question

我已按照guide 向 IPrincipal 添加自定义属性。

protected void Application_PostAuthenticateRequest(Object sender, EventArgs e)
    {
        HttpCookie authCookie = Request.Cookies[FormsAuthentication.FormsCookieName];
        if (authCookie != null)
        {
            FormsAuthenticationTicket authTicket = FormsAuthentication.Decrypt(authCookie.Value);
            JavaScriptSerializer serializer = new JavaScriptSerializer();
            CustomPrincipalSerializeModel serializeModel = serializer.Deserialize<CustomPrincipalSerializeModel>(authTicket.UserData);
            CustomPrincipal newUser = new CustomPrincipal(authTicket.Name);
            newUser.UserId = serializeModel.UserId;
            newUser.FirstName = serializeModel.FirstName;
            newUser.LastName = serializeModel.LastName;
            HttpContext.Current.User = newUser; /This line makes an error.
        }
    }

这是出错的最后一行。

无法将类型“SocialMedia.Models.CustomPrincipal”隐式转换为“System.Security.Principal.IPrincipal”。存在显式转换（您是否缺少演员表？）

为什么它不工作可能是什么问题？

Answer 1

错误很明显，您分配给User 属性的实例需要IPrincipal 类型的实例，我怀疑您的CustomPrincipal 类不是从IPrinicipal 接口继承的，那是因为您看到的是错误。

Answer 2

将最后一行改为：

HttpContext.Current.User = (IPrincipal)newUser;

编辑

确保ICustomPrincipal 扩展了IPrincipal 接口。