Month: February 2009

Kiwi Pie

Here’s a little recipe which I tried out last Sunday. The result was the Kiwi Pie on the picture below.

200g Flour
½pckg Baking Powder
50g Sugar
50g Butter
1 Egg
3spn Milk
6pcs Kiwi

Mix the flour with the baking powder and sugar in a bowl. Add the butter, egg and milk and knead the dough. Heat the oven up to 200°C. Lay out the dough in a spring form (around 24cm ∅). Peel the Kiwis and cut them into slices. Lay out the slices and bake the pie for about 20 minutes.

I actually also took some powdered sugar and lemon juice to mix some icing which I put over the pie. But you should wait with that until the pie has cooled down.

Kiwi-Pie

User Search in AD

I stumbled upon the System.DirectoryServices.AccountManagement namespace this week. It was introduced with .Net 3.5 and offers functionality to perform queries on AD objects like users, groups and computers in a more comfortable way than through the DirectorySearcher class from the System.DirectoryServices namespace. To illustrate the ease of using these classes, I came up with a tiny example which lists all users whose account name (the samAccountName attribute in AD) starts with an 'a'. On top of this, using LINQ it is quite simple to convert the resulting PrincipalSearchResult<Principal> collection into an IEnumerable<UserPrincipal>. 

using System;
using System.Collections.Generic;
using System.DirectoryServices.AccountManagement;
using System.Linq;

namespace UserSearch
{
    class Program
    {
        static void Main(string[] args)
        {
            PrincipalContext context = new PrincipalContext(ContextType.Domain, "contoso.com");

            UserPrincipal searchFilter = new UserPrincipal(context);
            searchFilter.SamAccountName = "a*";

            PrincipalSearcher ps = new PrincipalSearcher(searchFilter);

            IEnumerable<UserPrincipal> results = from principal in ps.FindAll()
                                                 where principal is UserPrincipal
                                                 select principal as UserPrincipal;

            foreach (UserPrincipal user in results)
            {
                Console.WriteLine("User '{0}' ({1}) Info:", user.SamAccountName, user.Name);
                Console.WriteLine("    Password Set On  {0}", user.LastPasswordSet);
                Console.WriteLine("    Last Log On      {0}", user.LastLogon);
                Console.WriteLine();
            }
        }
    }
}

Fun with JSON and WCF, Part II

Following the web app I mentioned in Fun with JSON and WCF (Part I), I ran into another issue with WCF hosted in IIS and serving the callers through JSON objects. My application uses integrated windows authentication to authenticate the users and grant / deny access based on the given credentials. Therefore, I have turned off anonymous access for the entire virtual directory the application is running in and turned on integrated windows authentication. Now when invoking the JSON service, I get the following exception.

[NotSupportedException: Security settings for this service require 'Anonymous' Authentication but it is not enabled for the IIS application that hosts this service.]
   System.ServiceModel.Channels.HttpChannelListener.ApplyHostedContext(VirtualPathExtension virtualPathExtension, Boolean isMetadataListener) +11453217
   System.ServiceModel.Activation.VirtualPathExtension.ApplyHostedContext(TransportChannelListener listener, BindingContext context) +75
   System.ServiceModel.Channels.HttpTransportBindingElement.BuildChannelListener(BindingContext context) +119
   System.ServiceModel.Channels.BindingContext.BuildInnerChannelListener() +66
   System.ServiceModel.Channels.MessageEncodingBindingElement.InternalBuildChannelListener(BindingContext context) +67
   System.ServiceModel.Channels.WebMessageEncodingBindingElement.BuildChannelListener(BindingContext context) +47
   System.ServiceModel.Channels.BindingContext.BuildInnerChannelListener() +66
[...]

This indicates that according to the configuration of the service binding, anonymous access is to be allowed however IIS does not allow it. Apart from the fact that I don’t understand in the first place, why the service would care about this (if it was the other way around, I’d understand), fixing it is simple. It again requires changes in the Web.config, like follows.

<configuration>
    <!-- ... -->
    <system.serviceModel>
        <behaviors>
            <!-- ... -->
        </behaviors>
        <serviceHostingEnvironment aspNetCompatibilityEnabled="true" />
        <services>
            <service behaviorConfiguration="MyServiceTypeBehavior" name="MyService">
                <endpoint address="" behaviorConfiguration="MyServiceAspNetAjaxBehavior"
                          binding="webHttpBinding" bindingConfiguration="ServiceAuth"
                          contract="MyService" />
            </service>
        </services>
        <bindings>
            <webHttpBinding>
                <binding name="ServiceAuth">
                    <security mode="TransportCredentialOnly">
                        <transport clientCredentialType="Windows"/>
                    </security>
                </binding>
            </webHttpBinding>
        </bindings>
    </system.serviceModel>
</configuration>

The bindingConfiguration attribute on line 11 refers to the new webHttpBinding definition from lines 17 to 21. Client authentication is there specified to be integrated windows authentication.

Fun with JSON and WCF

One of the projects I am working on at home is something like a media player web application which I use to listen to my favorite music from anywhere. It has a backend database which keeps the music files in a way which allows fast search on information about the files from the tags in the files. The files are then played in a handcrafted media player written in Silverlight 2.0. This being a fancy web 2.0 application, I use AJAX to search the database and return the results as JSON objects. Luckily enough, WCF supports you with this since .net 3.5. All you basically need to do is create a WCF service for your web project in Visual Studio 2008 (SP1). Then you even have IntellliSense support for the client side wrapper of the service, which of course gets generated automatically. On top of this, you do not have to care too much about inter-browser compatibility: The generated scripts with the base libraries work fine with both IE and Firefox.

If on the other hand, you are running the application on a virtual site in IIS which supports multiple host headers (let’s say: foo.bar.com and www.foo.bar.com) you’re likely to run into an exception like the following.

[ArgumentException: This collection already contains an address with scheme http. There can be at most one address per scheme in this collection.
Parameter name: item]
   System.ServiceModel.UriSchemeKeyedCollection.InsertItem(Int32 index, Uri item) +11520590
   System.Collections.Generic.SynchronizedCollection`1.Add(T item) +67
   System.ServiceModel.UriSchemeKeyedCollection..ctor(Uri[] addresses) +49
   System.ServiceModel.ServiceHost..ctor(Type serviceType, Uri[] baseAddresses) +129
   System.ServiceModel.Activation.ServiceHostFactory.CreateServiceHost(Type serviceType, Uri[] baseAddresses) +28
   System.ServiceModel.Activation.ServiceHostFactory.CreateServiceHost(String constructorString, Uri[] baseAddresses) +331
   System.ServiceModel.HostingManager.CreateService(String normalizedVirtualPath) +11659932
   System.ServiceModel.HostingManager.ActivateService(String normalizedVirtualPath) +42
   System.ServiceModel.HostingManager.EnsureServiceAvailable(String normalizedVirtualPath) +479

This indicates that a binding address which starts with http is already in use, when trying to automatically add the second address. The solution to this is as simple as updating your Web.Config file like shown here. Please take a look at line #9:

<configuration>
    <!-- ... -->
    <system.serviceModel>
        <behaviors>
            <!-- ... -->
        </behaviors>
        <serviceHostingEnvironment aspNetCompatibilityEnabled="true">
            <baseAddressPrefixFilters>
                <add prefix="http://foo.bar.com" />
            </baseAddressPrefixFilters>
        </serviceHostingEnvironment>
        <services>
            <!-- ... -->
        </services>
        <bindings>
            <!-- ... -->
        </bindings>
    </system.serviceModel>
</configuration>

Addendum from Feb 6: Apparently I was not entirely correct about using the service on a site with multiple host headers. While the above changes to Web.config fix the initial problem, they introduce a new problem. You’ll realize that this will work only for the requests using one of the host headers. The request to the service using the other host headers will throw a 404. This is a reported bug and will hopefully be fixed soon.