c#

6 posts

Beware of Enum.TryParse

What do you think Enum.TryParse will return when running this code?

public enum ContactMethod  
{
   Unknown = 0,
   Email = 1,
   Phone = 2
}

var result = Enum.TryParse("10", out ContactMethod contactMethod);  

"It will return false of course, 10 is not a valid value!!"

Wrong. It will return true. And even worse, the output variable contactMethod will have the value of...10!

Don't believe me? See it for yourself (dotnetfiddle)

Now, imagine that some developer wrote the following program:

public class Program  
{
    public static void Main(string args[])
    {
        var result = Enum.TryParse(args[0], out NukeStatus nukeStatus);
        FireNuke((int)nukeStatus);
    }

    public static void FireNuke(int status)
    {
        if(status == 0)
        {
           return;
        }

        if(status > 0 && status <= 10)
        {
           Console.WriteLine("TEST FIRING");
           TestFire();
        }

        if(status >= 15)
        {
           Console.WriteLine("NUKE EM ALL!");
           NukeEmAll();
        }
    }
}

public enum NukeStatus  
{
   Idle = 0,
   TestFireOneMissile = 5,
   TestFireAllMissiles = 10,
   FireOneMissile = 15,
   FireAllMissiles = 20
}

Now imagine that someone with fat fingers should do a test run and slips on the keyboard, so instead of passing in 10, 100 will be passed in instead.

dotnet run TrumpNukeProgram 100  

BOOM

Now, I know that my example is really stupid and the code is really bad, but still, it could happen!

What to use instead of Enum.TryParse then?

Note, this is only a problem when you try to pass in numeric values to TryParse.
If you want to be sure that your (int)value really exists in the Enum, you could use Enum.IsDefined instead.
Something like this:

var nukeStatusAsString = "100";  
var myNukeStatus = int.Parse(nukeStatusAsString); // Yeah yeah, error checking I know.  
var isDefined = Enum.IsDefined(typeof(NukeStatus), myNukeStatus);  
if (!isDefined)  
{
    return NukeStatus.Idle;
}
return (NukeStatus)myNukeStatus;  

You can read more about this here (Stackoverflow) and here (Microsoft).

JOS.ContentJson gets replaced by JOS.ContentSerializer

I've spent some time rebuilding the JOS.ContentJson library from scratch and when doing that I realised that it was kind of dumb to limit the library to only JSON. So I've added the possibility to replace the default serializer with a custom one, so you can return the data in any format you like(you have to build the serializer yourself though, I only provide a JSON serializer out of the box). By doing that, the name ContentJson looks kind of lame, so I've released a new package named JOS.ContentSerializer instead.

You can install it by doing Install-Package JOS.ContentSerializer
If you are using the JOS.ContentJson package, you will see that I've released a new major version, 3.0. I've marked many of the methods obsolete and I've also added a readme.txt that tells you to uninstall the package and install the new one instead.

One thing that's great(and bad) with this rewrite is that I could remove/refactor whatever I wanted so it's possible that I've removed something that you guys where using. I can't be sure since everything was based on extension methods in the old library which kind of makes it impossible for me to know which breaking changes I might have introduced, hence the new major version.

Another great thing is that the library now uses dependency injection everywhere, so it's extremely easy to customize the behavior. You can find the code and a more detailed README here.

If I've removed anything you were using, please create a new issue on GitHub and I will fix it asap.

Quick example

Consider the following pagetype:

public class DemoPage : PageData  
{
    [CultureSpecific]
    [Display(
        Name = "String",
        GroupName = SystemTabNames.Content,
        Order = 100)]
    public virtual string String { get; set; }

    [CultureSpecific]
    [Display(
        Name = "ContentArea",
        GroupName = SystemTabNames.Content,
        Order = 200)]
    public virtual ContentArea MainContentArea { get; set; }

    [CultureSpecific]
    [Display(
        Name = "Degrees",
        GroupName = SystemTabNames.Content,
        Order = 300)]
    public virtual double Degrees { get; set; }

    [CultureSpecific]
    [Display(
        Name = "Int",
        GroupName = SystemTabNames.Content,
        Order = 400)]
    public virtual int Int { get; set; }

    [CultureSpecific]
    [Display(
        Name = "Date",
        GroupName = SystemTabNames.Content,
        Order = 500)]
    public virtual DateTime DateTime { get; set; }

    [CultureSpecific]
    [Display(
        Name = "Bool",
        GroupName = SystemTabNames.Content,
        Order = 600)]
    public virtual bool Bool { get; set; }

    [CultureSpecific]
    [Display(
        Name = "PageType",
        GroupName = SystemTabNames.Content,
        Order = 700)]
    public virtual PageType PageType { get; set; }

    [CultureSpecific]
    [Display(
        Name = "ContentReference",
        GroupName = SystemTabNames.Content,
        Order = 800)]
    public virtual ContentReference ContentReference { get; set; }

    [CultureSpecific]
    [Display(
        Name = "PageReference",
        GroupName = SystemTabNames.Content,
        Order = 900)]
    public virtual PageReference PageReference { get; set; }

    [CultureSpecific]
    [Display(
        Name = "Url",
        GroupName = SystemTabNames.Content,
        Order = 1000)]
    public virtual Url Url { get; set; }

    [Display(
        Name = "InternalBlock",
        GroupName = SystemTabNames.Content,
        Order = 1100)]
    public virtual VimeoVideoBlock InternalBlock { get; set; }

    [Display(
        Name = "ContentReferenceList",
        GroupName = SystemTabNames.Content,
        Order = 1200)]
    public virtual IList<ContentReference> ContentReferenceList { get; set; }

    [Display(
        Name = "XhtmlString",
        GroupName = SystemTabNames.Content,
        Order = 1300)]
    public virtual XhtmlString XhtmlString { get; set; }

    [Display(
        Name = "LinkItemCollection",
        GroupName = SystemTabNames.Content,
        Order = 1400)]
    public virtual LinkItemCollection LinkItemCollection { get; set; }

    [Display(
        Name = "SelectOne",
        GroupName = SystemTabNames.Content,
        Order = 1500)]
    [SelectOne(SelectionFactoryType = typeof(ContactPageSelectionFactory))]
    public virtual string SelectOne { get; set; }

    [Display(
        Name = "SelectMany",
        GroupName = SystemTabNames.Content,
        Order = 1600)]
    [SelectMany(SelectionFactoryType = typeof(ContactPageSelectionFactory))]
    public virtual string SelectMany { get; set; }
}

By calling .ToJson on it like this

public class DemoPageController : PageController<DemoPage>  
{
    public string Index(DemoPage currentPage)
    {
        return currentPage.ToJson();
    }
}

You would get the following result

{
    "string": "This is a string",
    "mainContentArea": {
        "vimeoVideoBlock": [{
            "name": "My Vimeo Block"
        }]
    },
    "degrees": 133.7,
    "int": 1337,
    "dateTime": "2017-05-18T00:00:00+02:00",
    "bool": true,
    "pageType": "DemoPage",
    "contentReference": "http://localhost:52467/about-us/management/",
    "pageReference": "http://localhost:52467/alloy-plan/download-alloy-plan/",
    "url": "http://localhost:52467/globalassets/alloy-meet/alloymeet.png",
    "internalBlock": {
        "name": "Im a Vimeo block",
        "mainContentArea": {
            "youtubeVideoBlock": [{
                "name": "I am a youtube block in a contentarea on a Vimeoblock"
            }]
        }
    },
    "contentReferenceList": ["http://localhost:52467/search/", "http://localhost:52467/alloy-meet/"],
    "xhtmlString": "<p>I am a xhtmlstring, do you like it?</p>\n<p>Im <strong>bold not <em>bald</em></strong></p>",
    "linkItemCollection": [{
        "href": "http://localhost:52467/alloy-plan/?query=any",
        "title": "Any title",
        "target": "_blank",
        "text": "Any text"
    }, {
        "href": "https://josef.guru",
        "title": "External link",
        "target": "_blank",
        "text": "External"
    }, {
        "href": "mailto:[email protected]",
        "title": "Email link",
        "target": null,
        "text": "Email"
    }],
    "selectOne": [{
        "selected": false,
        "text": "Amar Gupta",
        "value": "34"
    }, {
        "selected": false,
        "text": "Fiona Miller",
        "value": "33"
    }, {
        "selected": true,
        "text": "Michelle Hernandez",
        "value": "30"
    }, {
        "selected": false,
        "text": "Robert Carlsson",
        "value": "32"
    }, {
        "selected": false,
        "text": "Todd Slayton",
        "value": "31"
    }],
    "selectMany": [{
        "selected": false,
        "text": "Amar Gupta",
        "value": "34"
    }, {
        "selected": true,
        "text": "Fiona Miller",
        "value": "33"
    }, {
        "selected": false,
        "text": "Michelle Hernandez",
        "value": "30"
    }, {
        "selected": false,
        "text": "Robert Carlsson",
        "value": "32"
    }, {
        "selected": false,
        "text": "Todd Slayton",
        "value": "31"
    }]
}

Custom Episerver routes without querystring - IPartialRouter

I will show you how to easily bind parameters to your action methods without using the querystring.

I have a page, MyPage, with a action method that looks like this:

public async Task<ActionResult> Index(MyPage currentPage, int myId)  
{
    var response = await this.thirdPartyApi.Get(myId);
    // Do something with the response and return a view
    var model = MyModel.Create(response);
    return View(model);        
}

I've also created the page in editmode, I named it MyExamplePage so I can access it like this: https://example.com/MyExamplePage

So, in order to populate the myId parameter I can call my page like this:

https://example.com/MyExamplePage?myId=1337

Asp.net will automatically populate the myId parameter from the querystring and everything works just fine, great. But, the URL looks kinda ugly, don't you think?

I want it to look like this instead: https://example.com/MyExamplePage/1337

This doesn't work right out the box, we will need to write some code. I got some great help from Johan Björnfot in this thread over at Episerver World.

It's actually really easy to make this work, here's what you will need to do:

  1. Create a class that inherits from IPartialRouter<MyPage, MyPage>
  2. Implement GetPartialVirtualPath and RoutePartial. In my case I was only interested in the RoutePartial method so I just returned null in GetPartialVirtualPath
  3. Extract and parse/validate the values in the RoutePartial method.
  4. Return the content.
  5. Register the partialrouter in Global.asax(or wherever you configure your routes). routes.RegisterPartialRouter(new ParameterPartialRouter());
  6. Done!

Here's the full code of my PartialRouter.

public class ParameterPartialRouter : IPartialRouter<MyPage, MyPage>
{
    public PartialRouteData GetPartialVirtualPath(
        MyPage content,
        string language,
        RouteValueDictionary routeValues,
        RequestContext requestContext)
    {
        return null;
    }

    public object RoutePartial(
        MyPage content,
        SegmentContext segmentContext)
    {
        var nextValue = segmentContext.GetNextValue(segmentContext.RemainingPath);
        int myId;
        if (Int32.TryParse(nextValue.Next, out myId))
        {
            segmentContext.RouteData.Values["myId"] = myId;
            segmentContext.RemainingPath = nextValue.Remaining;
        }
        return content;
    }
}