ASP.NET MVC - ActionFilterAttribute to validate POST data

Question

Actually I have an application that is using a WebService to retrieve some clients information. So I was validating the login information inside my ActionResult like:

[AcceptVerbs(HttpVerbs.Post)]
public ActionResult ClientLogin(FormCollection collection)
{
    if(Client.validate(collection["username"], collection["password"]))
    {
        Session["username"] = collection["username"];
        Session["password"] = collection["password"];
        return View("valid");
    }
    else
    {
       Session["username"] = "";
       Session["password"] = "";
       return View("invalid");
    }
}

Where Client.Validate() is a method that returns a boolean based on the information provided on the POST username and password

But I changed my mind and I would like to use that nice ActionFilterAttributes at the beginning of the method so it will just be rendered if the Client.validate() return true, just the same as [Authorize] but with my custom webservice, so I would have something like:

[AcceptVerbs(HttpVerbs.Post)]
[ValidateAsClient(username=postedUsername,password=postedPassword)]
//Pass Posted username and password to ValidateAsClient Class
//If returns true render the view
public ActionResult ClientLogin()
{
    return View('valid')
}

and then inside the ValidateAsClient I would have something like:

public class ValidateAsClient : ActionFilterAttribute
{
    public string username { get; set; }
    public string password { get; set; }

    public Boolean ValidateAsClient()
    {
        return Client.validate(username,password);
    }
}

So my problem is, I don't know exactly how to make it work, because I don't know how to pass the POSTED information to the [ValidateAsClient(username=postedUsername,password=postedPassword)] and also, how could I make the function ValidateAsClient work properly?

I hope this is easy to understand Thanks in advance

Answer 1

Something like this probably:

[AttributeUsage(AttributeTargets.All)]
public sealed class ValidateAsClientAttribute : ActionFilterAttribute
{
    private readonly NameValueCollection formData;
    public NameValueCollection FormData{ get { return formData; } }

    public ValidateAsClientAttribute (NameValueCollection formData)
    {
        this.formData = formData;
    }

    public override void OnActionExecuting
               (ActionExecutingContext filterContext)
    {
        string username = formData["username"];
        if (string.IsNullOrEmpty(username))
        {
             filterContext.Controller.ViewData.ModelState.AddModelError("username");
        }
        // you get the idea
    }
}

And use it like this:

[ValidateAsClient(HttpContext.Request.Form)]