Set custom IIdentity or IPrincipal

I need to do something fairly simple: in my ASP.NET MVC application, I want to set a custom IIdentity / IPrincipal. Whichever is easier / more suitable. I want to extend the default so that I can call something like User.Identity.Id and User.Identity.Role . Nothing fancy, just some extra properties.

I've read tons of articles and questions but I feel like I'm making it harder than it actually is. I thought it would be easy. If a user logs on, I want to set a custom IIdentity. So I thought, I will implement Application_PostAuthenticateRequest in my global.asax. However, that is called on every request, and I don't want to do a call to the database on every request which would request all the data from the database and put in a custom IPrincipal object. That also seems very unnecessary, slow, and in the wrong place (doing database calls there) but I could be wrong. Or where else would that data come from?

So I thought, whenever a user logs in, I can add some necessary variables in my session, which I add to the custom IIdentity in the Application_PostAuthenticateRequest event handler. However, my Context.Session is null there, so that is also not the way to go.

I've been working on this for a day now and I feel I'm missing something. This shouldn't be too hard to do, right? I'm also a bit confused by all the (semi)related stuff that comes with this. MembershipProvider , MembershipUser , RoleProvider , ProfileProvider , IPrincipal , IIdentity , FormsAuthentication .... Am I the only one who finds all this very confusing?

If someone could tell me a simple, elegant, and efficient solution to store some extra data on a IIdentity without all the extra fuzz.. that would be great! I know there are similar questions on SO but if the answer I need is in there, I must've overlooked.

Here's how I do it.

I decided to use IPrincipal instead of IIdentity because it means I don't have to implement both IIdentity and IPrincipal.

interface ICustomPrincipal : IPrincipal
{
    int Id { get; set; }
    string FirstName { get; set; }
    string LastName { get; set; }
}

public class CustomPrincipal : ICustomPrincipal
{
    public IIdentity Identity { get; private set; }
    public bool IsInRole(string role) { return false; }

    public CustomPrincipal(string email)
    {
        this.Identity = new GenericIdentity(email);
    }

    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

public class CustomPrincipalSerializeModel
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
}

if (Membership.ValidateUser(viewModel.Email, viewModel.Password))
{
    var user = userRepository.Users.Where(u => u.Email == viewModel.Email).First();

    CustomPrincipalSerializeModel serializeModel = new CustomPrincipalSerializeModel();
    serializeModel.Id = user.Id;
    serializeModel.FirstName = user.FirstName;
    serializeModel.LastName = user.LastName;

    JavaScriptSerializer serializer = new JavaScriptSerializer();

    string userData = serializer.Serialize(serializeModel);

    FormsAuthenticationTicket authTicket = new FormsAuthenticationTicket(
             1,
             viewModel.Email,
             DateTime.Now,
             DateTime.Now.AddMinutes(15),
             false,
             userData);

    string encTicket = FormsAuthentication.Encrypt(authTicket);
    HttpCookie faCookie = new HttpCookie(FormsAuthentication.FormsCookieName, encTicket);
    Response.Cookies.Add(faCookie);

    return RedirectToAction("Index", "Home");
}

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.Id = serializeModel.Id;
        newUser.FirstName = serializeModel.FirstName;
        newUser.LastName = serializeModel.LastName;

        HttpContext.Current.User = newUser;
    }
}

@((User as CustomPrincipal).Id)
@((User as CustomPrincipal).FirstName)
@((User as CustomPrincipal).LastName)

and in code:

    (User as CustomPrincipal).Id
    (User as CustomPrincipal).FirstName
    (User as CustomPrincipal).LastName

I think the code is self-explanatory. If it isn't, let me know.

Additionally to make the access even easier you can create a base controller and override the returned User object (HttpContext.User):

public class BaseController : Controller
{
    protected virtual new CustomPrincipal User
    {
        get { return HttpContext.User as CustomPrincipal; }
    }
}

and then, for each controller:

public class AccountController : BaseController
{
    // ...
}

which will allow you to access custom fields in code like this:

User.Id
User.FirstName
User.LastName

But this will not work inside views. For that you would need to create a custom WebViewPage implementation:

public abstract class BaseViewPage : WebViewPage
{
    public virtual new CustomPrincipal User
    {
        get { return base.User as CustomPrincipal; }
    }
}

public abstract class BaseViewPage<TModel> : WebViewPage<TModel>
{
    public virtual new CustomPrincipal User
    {
        get { return base.User as CustomPrincipal; }
    }
}

Make it a default page type in Views/web.config:

<pages pageBaseType="Your.Namespace.BaseViewPage">
  <namespaces>
    <add namespace="System.Web.Mvc" />
    <add namespace="System.Web.Mvc.Ajax" />
    <add namespace="System.Web.Mvc.Html" />
    <add namespace="System.Web.Routing" />
  </namespaces>
</pages>

and in views, you can access it like this:

@User.FirstName
@User.LastName

I can't speak directly for ASP.NET MVC, but for ASP.NET Web Forms, the trick is to create a FormsAuthenticationTicket and encrypt it into a cookie once the user has been authenticated. This way, you only have to call the database once (or AD or whatever you are using to perform your authentication), and each subsequent request will authenticate based on the ticket stored in the cookie.

A good article on this: http://www.ondotnet.com/pub/a/dotnet/2004/02/02/effectiveformsauth.html (broken link)

Edit:

Since the link above is broken, I would recommend LukeP's solution in his answer above: https://stackoverflow.com/a/10524305 - I would also suggest that the accepted answer be changed to that one.

Edit 2: An alternative for the broken link: https://web.archive.org/web/20120422011422/http://ondotnet.com/pub/a/dotnet/2004/02/02/effectiveformsauth.html

Here is an example to get the job done. bool isValid is set by looking at some data store (lets say your user data base). UserID is just an ID i am maintaining. You can add aditional information like email address to user data.

protected void btnLogin_Click(object sender, EventArgs e)
{         
    //Hard Coded for the moment
    bool isValid=true;
    if (isValid) 
    {
         string userData = String.Empty;
         userData = userData + "UserID=" + userID;
         FormsAuthenticationTicket ticket = new FormsAuthenticationTicket(1, username, DateTime.Now, DateTime.Now.AddMinutes(30), true, userData);
         string encTicket = FormsAuthentication.Encrypt(ticket);
         HttpCookie faCookie = new HttpCookie(FormsAuthentication.FormsCookieName, encTicket);
         Response.Cookies.Add(faCookie);
         //And send the user where they were heading
         string redirectUrl = FormsAuthentication.GetRedirectUrl(username, false);
         Response.Redirect(redirectUrl);
     }
}

in the golbal asax add the following code to retrive your information

protected void Application_AuthenticateRequest(Object sender, EventArgs e)
{
    HttpCookie authCookie = Request.Cookies[
             FormsAuthentication.FormsCookieName];
    if(authCookie != null)
    {
        //Extract the forms authentication cookie
        FormsAuthenticationTicket authTicket = 
               FormsAuthentication.Decrypt(authCookie.Value);
        // Create an Identity object
        //CustomIdentity implements System.Web.Security.IIdentity
        CustomIdentity id = GetUserIdentity(authTicket.Name);
        //CustomPrincipal implements System.Web.Security.IPrincipal
        CustomPrincipal newUser = new CustomPrincipal();
        Context.User = newUser;
    }
}

When you are going to use the information later, you can access your custom principal as follows.

(CustomPrincipal)this.User
or 
(CustomPrincipal)this.Context.User

this will allow you to access custom user information.

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