Question

在研究FormsAuthentication几天之后，我决定将一个序列化对象存储在FormsAuth cookie的UserData属性中，并为HttpContext.Current.User使用自定义IPrincipal对象。

我发现的大多数指南都说要将IPrincipal对象强制转换为你的对象。我每次都会得到一个无效的强制转换异常。我做错了什么？

MyUserData

public class MyUserData
{
    public long UserId { get; set; }
    public string Username { get; set; }
    public bool IsSuperUser { get; set; }
    public string UnitCode { get; set; }
    public string EmailAddress { get; set; }
    public List<string> Roles { get; set; }

    // Serialize    
    public override string ToString()
    {
        JavaScriptSerializer serializer = new JavaScriptSerializer();
        string result = serializer.Serialize(this);
        return result;
    }

    // Deserialize
    public static MyUserData FromString(string text)
    {
        JavaScriptSerializer serializer = new JavaScriptSerializer();
        return serializer.Deserialize<MyUserData>(text);
    }
}

CustomPlatformPrincipal

public class MyCustomPrincipal : IPrincipal
{
    public MyUserData MyUserData { get; set; }
    public IIdentity Identity { get; private set; }

    public MyCustomPrincipal(MyUserData myUserData)
    {
        MyUserData = myUserData;
        Identity = new GenericIdentity(myUserData.Username);
    }

    public bool IsInRole(string role)
    {
        return MyUserData.Roles.Contains(role);
    }
}

的Global.asax.cs

protected void Application_AuthenticateRequest(Object sender, EventArgs e)
    {
        HttpCookie authCookie = Context.Request.Cookies[FormsAuthentication.FormsCookieName];
        if (authCookie == null || authCookie.Value == "")
        {
            return;
        }

        FormsAuthenticationTicket authTicket;
        try
        {
            authTicket = FormsAuthentication.Decrypt(authCookie.Value);
        }
        catch
        {
            return;
        }

        if (Context.User != null)
        {
            // the from string deserializes the data
            MyUserData myUserData = MyUserData.FromString(authTicket.UserData);
            Context.User = new MyCustomPrincipal(myUserData);
        }
    }

我的页面

var myUserData = ((MyCustomPrincipal)(HttpContext.Current.User)).MyUserData;
// invalid cast exception (can't cast IPrincipal to MyCustomPrincipal)

我正在关注的文章：http://primaryobjects.com/CMS/Article147.aspx

所以似乎我获取数据的唯一方法是解密auth cookie，然后反序列化authCookie的userData字符串。

有什么建议吗？

更新

尝试遵循此SO问题的建议：Implementing a Custom Identity and IPrincipal in MVC

代码如下，但没有用。

[Serializable]
public class MyCustomPrincipal : IPrincipal, ISerializable
{
    public CustomUserData CustomUserData { get; set; }
    public IIdentity Identity { get; private set; }

    //public MyCustomPrincipal (IIdentity identity) { Identity = identity; }

    public MyCustomPrincipal(CustomUserData customUserData)
    {
        CustomUserData = customUserData;
        Identity = new GenericIdentity(customUserData.Username);
    }

    public bool IsInRole(string role)
    {
        return PlatformUserData.Roles.Contains(role);
    }


    public void GetObjectData(SerializationInfo info, StreamingContext context)
    {
        if (context.State == StreamingContextStates.CrossAppDomain)
        {
            MyCustomPrincipal principal = new MyCustomPrincipal (this.CustomUserData );
            info.SetType(principal.GetType());

            System.Reflection.MemberInfo[] serializableMembers;
            object[] serializableValues;

            serializableMembers = FormatterServices.GetSerializableMembers(principal.GetType());
            serializableValues = FormatterServices.GetObjectData(principal, serializableMembers);

            for (int i = 0; i < serializableMembers.Length; i++)
            {
                info.AddValue(serializableMembers[i].Name, serializableValues[i]);
            }
        }
        else
        {
            throw new InvalidOperationException("Serialization not supported");
        }
    }
}

Answer 1

你是否在调试模式下运行？您可以在HttpContext.Current.User上设置断点，您将看到该用户当时的类型。从您的Application_AuthenticateRequest方法，无法保证用户将是您期望的类型。在达到自定义类型设置之前，有许多退出点。甚至这段代码：Context.User！= null。你的期望是错误的。我没有详细介绍Context.User，但是，根据您的上下文，您期望Context.User是您的自定义用户。所以有效的检查应该是：

var custom = Context.Current as MyCustomPrinciple;
if(custom == null)
{
// Your construct code here.
}

我强烈建议：您需要进入调试模式，以确切了解发生了什么。

从HttpContext获取自定义IPrincipal时无效的强制转换

1 个答案: