when using Postal mail MVC 4 Razor Mobile View Engine generates error

Question

I am using postal mail to send an order confirmation. It is an MVC4 project. The code was sending email confirmations correctly.

Recently, I have added MVC mobile to the project. Everything works - except when sending a confirmation email when the user is on a mobile device. This is the order confirmation class:

    public class OrderConfirmation : Postal.Email
    {
        public string email { get; set; }
        public string partyid { get; set; }
        public string GrouponCode { get; set; }
        public string originalpartyDate { get; set; }
        public string originalpartyStartTime { get; set; }
        public string originalpartyTitle { get; set; }
        public string originalOrderDate { get; set; }
        public bool GrouponWasUpgraded { get; set; }
        public decimal GrouponFaceValue { get; set; }
        public bool ClassCancelled { get; set; }
        public string firstname { get; set; }
        public string orderlink { get; set; }
    }

And then it gets called like this:

ci = new Email.OrderConfirmation
{
    ClassCancelled = false,
    email = Email,
    firstname = FirstName,
    orderlink = "https://website.com/Checkout/Archive?orderlinkid=" + OrderLinkId,
    originalpartyDate = DateStart.ToShortDateString(),
    originalpartyStartTime = DateStart.ToShortTimeString(),
    originalpartyTitle = odt.Party.Title,
    partyid = odt.PartyId.ToString()
 };
 Task task = ci.SendAsync();

In my Global.asax.cs file I detect the mobile devices, and insert the display modes, like this:

   protected void Application_Start()
   {
   DisplayModeProvider.Instance.Modes.Insert(0, new
        DefaultDisplayMode("Tablet")
        {
            ContextCondition = (ctx =>
            ctx.Request.UserAgent.IndexOf("iPad", StringComparison.OrdinalIgnoreCase) >= 0 ||
            ctx.Request.UserAgent.IndexOf("Android", StringComparison.OrdinalIgnoreCase) >= 0 &&
            ctx.Request.UserAgent.IndexOf("mobile", StringComparison.OrdinalIgnoreCase) < 1)
        });
        DisplayModeProvider.Instance.Modes.Insert(1, new DefaultDisplayMode("iPhone")
            {
                ContextCondition = (ctx =>
                    ctx.GetOverriddenBrowser().IsMobileDevice ||
                    ctx.GetOverriddenUserAgent().IndexOf
                    ("iPhone", StringComparison.OrdinalIgnoreCase) >= 0
                    )
            });
     /// omitted the rest of the (standard) code for brevity
    }

The error message I get is a generic "Object reference not set to an instance of an object." I have put the stack trace below, as well as an image of when the error code is generated.

iisexpress.exe Error: 0 : 4/15/2014 11:09:33 AMSystem.NullReferenceException: Object reference not set to an instance of an object.
   at application.MvcApplication.<Application_Start>b__1(HttpContextBase ctx) in c:\Dropbox\SourceCode\PUYF_NonTFS\PUYF_Website\Application\Global.asax.cs:line 132
   at System.Web.WebPages.DefaultDisplayMode.CanHandleContext(HttpContextBase httpContext)
   at System.Web.WebPages.DisplayModeProvider.<>c__DisplayClass6.<GetAvailableDisplayModesForContext>b__5(IDisplayMode mode)
   at System.Linq.Enumerable.WhereListIterator`1.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at System.Web.Mvc.VirtualPathProviderViewEngine.GetPath(ControllerContext controllerContext, String[] locations, String[] areaLocations, String locationsPropertyName, String name, String controllerName, String cacheKeyPrefix, Boolean useCache, String[]& searchedLocations)
   at System.Web.Mvc.VirtualPathProviderViewEngine.FindView(ControllerContext controllerContext, String viewName, String masterName, Boolean useCache)
   at System.Web.Mvc.ViewEngineCollection.<>c__DisplayClassc.<FindView>b__a(IViewEngine e)
   at System.Web.Mvc.ViewEngineCollection.Find(Func`2 lookup, Boolean trackSearchedPaths)
   at System.Web.Mvc.ViewEngineCollection.FindView(ControllerContext controllerContext, String viewName, String masterName)
   at Postal.EmailViewRenderer.CreateView(String viewName, ControllerContext controllerContext)
   at Postal.EmailViewRenderer.Render(Email email, String viewName)
   at Postal.EmailService.CreateMailMessage(Email email)
   at Postal.EmailService.SendAsync(Email email)
   at Postal.Email.SendAsync()
   at Application.Models.Order.SendConfirmation(ArtStoreEntities dbcontext) in    
c:\Dropbox\SourceCode\PUYF_NonTFS\PUYF_Website\Application\Models\Order.cs:line 134

It seems, when postal is generating the view, it hits the application_start in the global.asax file, and because the useragent properties are null - it generates the error. I tried putting a try catch block around the specific code in the application_start procedure - but that does not work.

I need help how to tell MVC or Postal not to bother with the displaymodes. Any suggestions?

Answer 1

This is what I ended up doing:

    DisplayModeProvider.Instance.Modes.Insert(0, new
            DefaultDisplayMode("Tablet"){
        ContextCondition = (ctx =>
        ctx.Request.UserAgent != null &&
        (
        ctx.Request.UserAgent.IndexOf("iPad", StringComparison.OrdinalIgnoreCase) >= 0 ||
        ctx.Request.UserAgent.IndexOf("Android", StringComparison.OrdinalIgnoreCase) >= 0 &&
        ctx.Request.UserAgent.IndexOf("mobile", StringComparison.OrdinalIgnoreCase) < 1))
    });

    DisplayModeProvider.Instance.Modes.Insert(1, new DefaultDisplayMode("iPhone"){
        ContextCondition = (ctx =>
            ctx.Request.UserAgent != null &&
        (
            ctx.GetOverriddenBrowser().IsMobileDevice ||
            ctx.GetOverriddenUserAgent().IndexOf
            ("iPhone", StringComparison.OrdinalIgnoreCase) >= 0
            )
        )
    });

Answer 2

Could you try making the ContextCondition return false when ctx.Request.UserAgent is null?