无法转换类型＆＃39; CustomPrincipal＆＃39;到了System.Security.Principal.IPrincipal＆＃39;

Question

我已按照此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.
        }
    }

这是发生错误的最后一行。

  

无法隐式转换类型＆＃39; SocialMedia.Models.CustomPrincipal＆＃39;到了System.Security.Principal.IPrincipal＆＃39;。存在显式转换（您是否错过了演员？）

为什么它不起作用可能是什么问题。？

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继承的界面，那是因为你看到了错误。

Answer 2

将最后一行更改为：

HttpContext.Current.User = (IPrincipal)newUser;

修改

确保ICustomPrincipal扩展了IPrincipal界面。