The other day a colleague and I were trying to create a rule that validated two properties by querying the database and checking that the combination didn’t already exist. But we couldn’t seem to work it out.

I cheekily pinged @JeremySkinner and he helpfully pointed out that there are several ways of validating multiple properties:

• if you want to do cross property comparison then RuleFor(x => x.Foo).GreaterThan(x => x.Bar) etc
• you can also use Must: RuleFor(x => x.Foo).Must((instance, foo) => …)
• usually those cover most scenarios. If not, then there’s also Custom, but that’s usually a last resort

The second option was what worked for us, and here is an example.

public class FooBarRequestValidator : AbstractValidator<FooBarRequest>
{
    private readonly IRepository repository;

    public FooBarRequestValidator(IRepository repository)
    {
        this.repository = repository;

        RuleFor(x => x.Foo)
		.Must(NotAlreadyHaveABar)
		.WithMessage("You already have a bar for this foo.");
    }

    private bool NotAlreadyHaveABar(FooBarRequest instance, string foo)
    {
        return !repository.GetAll<FooBar>()
		.Any(x => x.Foo == foo && x.Bar == instance.Bar);
    }
}

The trick is using the overload of Must() that takes a Func<T, TProperty, bool> predicate: that gives you access to the whole instance for your validating pleasure. Here, in NotAlreadyHaveABar() I can access Bar even though the rule is for the Foo property.

This works with FluentValidation v1.1 up to v2.0 Beta 1.

This can be quite useful. However, you hit a snag if you try to host a WCF service in that site because WCF only allows a single address. Navigate to the service in your browser and you get the following error:

This collection already contains an address with scheme http. There can be at most one address per scheme in this collection.

Thankfully, in .NET 3.5 there is a very easy way of solving this problem. You can tell WCF which address to use by simply configuring a base address prefix filter in web.config.

<system.serviceModel>
  <serviceHostingEnvironment>
     <baseAddressPrefixFilters>
        <add prefix=”http://xyz.mysite.com”/>
    </baseAddressPrefixFilters>
  </serviceHostingEnvironment>
</system.serviceModel>

This config-only solution saved me from a real headache today as it meant that I didn’t have to recompile and redeploy. So, I thought I’d share it.

When trying to add a strongly-typed view I got the following error:

System.TypeLoadException: Could not load type ‘MyMvcApp.Shared.ISomeInterface’ from assembly ‘MyMvcApp.Domain, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null’.

The issue was that the model object implemented ISomeInterface, which was defined in a different assembly.

I think this is a reasonably common scenario: model objects often use attributes or implement interfaces from validation frameworks and the like – so I was surprised that this bug had slipped into the release candidate. However, A bit of experimentation showed that the problem doesn’t happen if the model object itself lives in the web app. So it’s only when the model object is in a separate assembly from the web app, and the dependency (in this case the interface) is in yet another assembly. Ok, so that makes it a little more of a fringe case. But I happen to be in this fringe!

Luckily for me, not only had the bug already been reported but someone had also posted a workaround: you can get it working by making the relevant assembly available to Visual Studio. All you need to do is find out where Visual Studio is looking.

The only problem with the proposed workaround is that it involved finding the temp folder Visual Studio is using, and that changes for each session, which is a bit of a pain.

Anyway, I ran up Process Monitor and found that one of the places Visual Studio was looking was:

%Program Files%\Microsoft Visual Studio 9.0\Common7\IDE\

Result! That location doesn’t change across Visual Studio sessions.

So all I had to do was copy the assembly (MyMvcApp.Shared.dll) to that folder and then it worked fine.

Hopefully this will be fixed in the eagerly anticipated RTM. But in the meantime this is a pretty good workaround.

Method not found: ‘FluentNHibernate.Mapping.IdentityPart`1<!0> FluentNHibernate.Mapping.ClassMap`1.Id(System.Linq.Expressions.Expression`1<System.Func`2<!0,System.Object>>)’.

I thought I’d post the (annoyingly simple) solution so that someone else might be saved the agony.

In my case, the FluentNHibernate.dll in one of my projects was an old version. Yawn.

NHibernate.HibernateException : Could not create the driver from NHibernate.Driver.SQLite20Driver, NHibernate, Version=2.0.0.4000, Culture=neutral, PublicKeyToken=aa95f207798dfdb4.

The IDbCommand and IDbConnection implementation in the assembly System.Data.SQLite could not be found.

I had checked to make sure the System.Data.SQLite.dll was copied to the application dir, so what gives?

Well it turns out that the SQLite.dll I was using was compiled for x86. To solve the problem you can either

1. Download the x64 version of System.Data.SQLite.dll, as suggested here, or
2. Just change the platform target of your project to x86. 

   

If the project really needs to take advantage of 64 bit then you’d go for option 1. However, option 2 is easier and, in my case, more pragmatic because it means the code will work on both x86 and x64 systems.

Hope this helps.

But for me the highlight of the keynotes was when Scott Guthrie mentioned that Silverlight is jumping “outside the browser”

“Next year we will also then be shipping a major new release of Silverlight, which includes a bunch of new runtime features.

“We’ve already announced support for H.264 media, and you’ll see a lot more media features being announced in the months ahead. In a few minutes you’ll learn about how you can actually run Silverlight both inside the browser, and now, OUTSIDE the browser. (applause)

“Also, as part of the next Silverlight release we’re going to be adding much richer graphics support as well as much improved data support.”

Of course, “in a few minutes” probably referred to a session on Silverlight, and as I wasn’t at the conference I’m left wondering about the details for now. Silverlight outside the browser really would deliver on Silverlight’s former name “WPF Everywhere”. It pits Silverlight against Adobe AIR and really ups the ante in the Rich Internet Application (RIA) space.

Of course, for this announcement to even mean anything, “outside the browser” must mean on both the Windows and the Mac desktop (and yes, the Linux desktops too although that’s technically ‘Moonlight’). After all, we already have Silverlight outside the browser on Windows – it’s full on WPF. So if Silverlight itself is jumping outside the browser I can only assume that this is the the long-awaited move to get the .NET Framework running on the Mac!

If this proves to be the case, it will have profound implications for technology choice on RIA projects, especially as offline capability starts to become more important. Silverlight will finally be a player – not just a media player.

• The next version of Windows server – which Ballmer dubbed Windows “Cloud” for want of a better word – will take cloud computing to the next level.
• When asked if MS will offer an Office-as-a-service product to compete with Google Apps, Ballmer said yes. However, he balked at using the term “compete” when talking about Google Apps, which he doesn’t regard as serious competition – and nor do I for what it’s worth. He said there would be a “click-to-run” Office Live type thing (I’m imagining Click-Once) as well as a cut-down, browser-only offering for when you want to do some “light editing at an internet café”.

The funniest thing was at the end of the keynote. Ballmer was asked if he would mind re-enacting his “monkey dance/developer, developer, developer” craziness. Being the good sport he is, he then lept about on the stage chanting “IT Pros, IT Pros, IT Pros…I LOVE IT PROS!!!!”.

The trip to the Southbank was worth it just for that.

For example, today I was doing some cross-browser testing and I wanted to have four different browsers open at the same time. The thing is, the browser windows were all over the place.

So, I wanted to tile them. You can do this by control-clicking all four taskbar items, right-clicking, and selecting “Tile Horizontally”.

The problem is, while Safari, FireFox and IE were happy to oblige, Google Chrome just wasn’t interested.

Not exactly sure why this doesn’t work, although I suspect it’s down to Google wanting to keep the code base as cross-platform as possible and in the process some Windows-specific things have fallen through the cracks. Perhaps I should be brave like Scott Hanselman and actually dive into the Chrome source code to find out.

What joy to find that Pete McGann and Richard Costall have created a Sliverlight version of Manic Miner! Have a play here:

http://www.nxtgenug.net/manicminer/

Usually this wouldn’t be too difficult, except that I’m using ASP.NET MVC, and for some reason the normal method isn’t available.

The normal method is to select an ASPX file and choose to Browse With…

VS then launches a dialog allowing you to select your default browser.

However, if you’re in an ASP.NET MVC project (Preview 3 at the time of writing), the “Browse With…” option isn’t there. One solution is to open a non-MVC project and do as above.

Another solution is to go directly to the file where VS stores this setting: “browsers.xml”. The file is in your user profile, mine was:

C:\Users\Stuart\App Data\Local\Microsoft Visual Studio\9.0\browsers.xml

Open the file in Visual Studio and then press Ctrl-K, Ctrl+D to format the document so that it is readable. Find the browser you want and set the <IsDefault> tag to True. Et voilà! Job done.

<?xml version="1.0"?>
<BrowserInfo>
  <Browser>
    <Name>Internet Explorer</Name>
    <Path>"C:Program FilesInternet Exploreriexplore.exe"</Path>
    <Resolution>0</Resolution>
    <IsDefault>True</IsDefault>
    <DDE>
      <Service>IExplore</Service>
      <TopicOpenURL>WWW_OpenURL</TopicOpenURL>
      <ItemOpenURL>"%s",,0xffffffff,3,,,,</ItemOpenURL>
      <TopicActivate>WWW_Activate</TopicActivate>
      <ItemActivate>0xffffffff,0</ItemActivate>
    </DDE>
  </Browser>
  <Browser>
    <Name>Firefox</Name>
    <Path>"C:Program FilesMozilla Firefoxfirefox.exe"</Path>
    <Resolution>0</Resolution>
    <IsDefault>False</IsDefault>
  </Browser>
  <InternalBrowser>
    <Resolution>0</Resolution>
    <IsDefault>False</IsDefault>
  </InternalBrowser>
</BrowserInfo>