How can get nullable string value?

Question

[HttpGet]
public ActionResult Login(string? returnUrl)
{
    if (Request.IsAuthenticated)
    {
        if(returnUrl.HasValue)
           return RedirectToAction("Index", "Home");
        else
           return RedirectToAction(returnUrl);
    }
    return View();
}

enter image description here

Error: The best overloaded method match for 'System.Web.Mbv.Controller.Redirect(string)' has some invalid arguments

How can use nullable string for RedirectToAction()

string is already nullable. string? doesn't make sense. What are you try to do exactly? — Soner Gönül
– Soner Gönül, Commented Nov 25, 2015 at 11:47

Stephen Brickner · Accepted Answer · 2015-11-25 11:52:26Z

7

String is nullable already but you can check for null with string.IsNullOrEmpty.

[HttpGet]
public ActionResult Login(string returnUrl)
{
        if (Request.IsAuthenticated)
        {
           if(string.IsNullOrEmpty(returnUrl))
           {
               return RedirectToAction("Index", "Home");
           }
           else
           {
               return RedirectToAction(returnUrl);
           }
        }
        return View();
}

You could also default it so if it's not passed in it will never be empty.

[HttpGet]
    public ActionResult Login(string returnUrl = "www.yourDomain.com/login")
    {
            if (Request.IsAuthenticated)
            {
               return RedirectToAction(returnUrl);
            }
            return View();
    }

answered Nov 25, 2015 at 11:52

Stephen Brickner

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