如何在ASP.NET MVC中实现自定义Principal和Identity？

// 自定义Principal类
public class CustomPrincipal : IPrincipal
{
    private IIdentity _identity;
    private string[] _roles;

    public CustomPrincipal(IIdentity identity, string[] roles)
    {
        _identity = identity;
        _roles = roles;
    }

    public IIdentity Identity => _identity;

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

// 自定义Identity类
public class CustomIdentity : IIdentity
{
    private string _name;
    private string _authenticationType;

    public CustomIdentity(string name, string authenticationType)
    {
        _name = name;
        _authenticationType = authenticationType;
    }

    public string AuthenticationType => _authenticationType;

    public bool IsAuthenticated => !string.IsNullOrEmpty(_name);

    public string Name => _name;
}

// Global.asax文件中的Application_PostAuthenticateRequest事件
protected void Application_PostAuthenticateRequest(object sender, EventArgs e)
{
    // 获取当前用户的认证信息，可以根据实际情况进行修改
    string username = HttpContext.Current.User.Identity.Name;
    string[] roles = GetRolesForUser(username);

    // 创建自定义的Principal对象
    CustomIdentity identity = new CustomIdentity(username, "Forms");
    CustomPrincipal principal = new CustomPrincipal(identity, roles);

    // 将自定义的Principal对象赋值给HttpContext.Current.User属性
    HttpContext.Current.User = principal;
}