The art of simplicity

If you ever build an MVVM style application before(using WPF, Silverlight, UWP,…) you probably used the ObservableCollection class.  It implements the INotifyCollectionChanged interface and can be seen as the counterpart of INotifyPropertyChanged. Through this interface the ObservableCollection notifies its subscribers about items being added, deleted, moved, … Unfortunately the ObservableCollection is rather limited in it’s behavior and doesn’t fit well in a truely observable architecture. Luckily the ReactiveUI framework and more specificly the ReactiveList solve exactly this problem… Let’s describe a scenario I had to build that was hard to do using ObservableCollection and a walk-in-the-park with ReactiveList: In our application we have to show a list of alerts and update the list when new alerts arrive. However alerts can arrive at a high pace and we don’t want to update the UI continuously but only when at least 5 alerts are raised. In our original implementat...

We as software developers love technology, especially new and shiny stuff. When it comes to building software we always want to play with the latest tool, technology and architecture of the day. And for a part that’s OK, as it drives innovation and creates new opportunities but for a part it is not as we have a tendency to over-engineer and try to stuff as many of these new and shiny things into our pour software projects. “Don’t over-engineer” is a golden rule that we all should apply. A great post that perfectly relates to this sentiment is “ 10 Modern Software Over-Engineering Mistakes ”, a must read!

If you already tried to create your first Angular 2 application, you probably had the same experience as I had. It takes a lot of time before all building blocks, configuration settings, npm packages, webpack, system.js,… is finally configured in a way that works. Once you’ve passed this initial roadblock, you are good to go, but it will take some time to get there… Luckily Mads Kristensen, the guy who brought us the great Web Essentials extensions for Visual Studio, created the ASP.NET Core Template Pack . It is a collection of project templates that makes it easy to learn how to use ASP.NET Core. Among the templates you can find one specific for ASP.NET Core and Angular 2. Let’s try it! Download and install the ASP.NET Core Template Pack either from the Visual Studio Gallery or through the Extensions and Updates… inside Visual Studio. Note that .NET Core Tooling Preview 2 or later is required. Open Visual Studio . Go to File –> New Project . ...

After configuring my ASP.NET MVC application to use WSFederation with WIF, I was finally ready to run the app the first time. However instead of redirecting me to the configured STS and showing me a login page I ended up with a 401 Unauthorized error page. I first thought that the required HTTP modules were missing, but no they were there: Let’s have a look at the WIF configuration: There is definetely something wrong here, but I had a hard time figuring out what. The problem is related to the passiveRedirectEnabled configuration setting. If you set passiveRedirectEnabled to false , WIF will no longer be responsible for the redirections to your issuers. That explained a lot! Switching the setting to true solved my issue and I was finally welcomed by my STS login page…

I’m currently working on a training for one of my customers covering WIF(Windows Identity Foundation),  OIDC(Open ID Connect) and some other security related topics on top of the .NET stack. Yesterday I got a strange problem after configuring the MVC application that should act as the relying party. Here is the WIF specific configuration: And here is the error I got when I ran the application: ID4175: The issuer of the security token was not recognized by the IssuerNameRegistry. To accept security tokens from this issuer, configure the IssuerNameRegistry to return a valid name for this issuer. I compared the thumbprint of the certificate used by the STS with the thumbprint inside the config: <trustedIssuers>          <add thumbprint=" 6b 7a cc 52 03 05 bf db 4f 72 52 da eb 21 77 cc 09 1f aa e1 " /> </trustedIssuers> No matter how much I looked, I couldn’t see a differe...

Last week I discovered a new tab inside VSTS; the Usage tab.   The Usage tab shows the request history of the users ordered by usage( based on Team Services Throughput Units  or TSTUs). By default, visiting the Usage page will display requests for the last hour. Another nice feature is that you can review the request history leading up to delayed requests.

When we tried to deploy a Xamarin Forms app to an Android device, we got the following error: Xamarin.AndroidTools.AndroidDeploymentException: InternalError ---> Mono.AndroidTools.InstallFailedException: Failure [INSTALL_FAILED_UPDATE_INCOMPATIBLE] at Mono.AndroidTools.Internal.AdbOutputParsing.CheckInstallSuccess(String output, String packageName) at Mono.AndroidTools.AndroidDevice.<>c__DisplayClass2a.<InstallPackage>b__29(Task`1 t) at System.Threading.Tasks.ContinuationTaskFromResultTask`1.InnerInvoke() at System.Threading.Tasks.Task.Execute() --- End of inner exception stack trace --- at Xamarin.AndroidTools.AndroidDeploySession.RunLogged(CancellationToken token) at Xamarin.AndroidTools.AndroidDeploySession.Start(CancellationToken token) The problem seemed to be that a "ghost" copy of the app still existed on the device although there was no app icon. However when searching under Applications we found it with ...

I hear people talk about JavaScript fatigue, the constant churn of new frameworks, tools and libraries in the JavaScript ecosystem makes it difficult to keep up. I must say that I have the same feelings regarding Cloud, every week Microsoft, Google or Amazon announce a new PaaS, SaaS, FaaS,… offering. A great resource to help you understand what’s going on inside the Amazon cloud space, is the Open Guide to Amazon Webservices . From the github page: A lot of information on AWS is already written. Most people learn AWS by reading a blog or a “ getting started guide ” and referring to the standard AWS references . Nonetheless, trustworthy and practical information and recommendations aren’t easy to come by. AWS’s own documentation is a great but sprawling resource few have time to read fully, and it doesn’t include anything but official facts, so omits experiences of engineers. The information in blogs or Stack Overflow is also not consistently up to date. This guide is by...

A colleague came to me with the following NHibernate problem; he loads some data from the database using the QueryOver syntax. Although he doesn’t do anything else with the data, NHibernate detects that the list is changed and tries to flush the changes to the database. What’s causing NHibernate to think that an item has changed? We figured out the reason after some investigation. Inside our database we have nullable column e.g.: Age [int] NULL -- Nullable column But inside the mapping we decided to map it to a not nullable property: <property name="Age" /> public virtual int Age { get; set; } The moment that the data is loaded and NHibernate sees a null value for Age, inside the property it will be set to 0(the default value for an int). As the value has changed, NHibernate will detect this and tries to flush the change afterwards. The solution is to make the property nullable: public virtual int? Age { get; set; }

Although Akka.NET has built-in support for testing , it is sometimes hard to find out what’s really going on inside your actor system. A useful feature that can help you solve this problem during integration testing is the EventFilter . The EventFilter is a tool to verify that actors write certain log messages. It can also detect if messages go to DeadLetters and if certain exceptions are thrown . 2 examples: Remark: By default the event filter searches for exact matches.

With the introduction of TypeScript 2.0 one of the biggest root causes of bugs in software development finally got a solution. TypeScript 2.0 adds the ability to treat every type as non-nullable. Let’s see how this works! Installing TypeScript 2.0 Before we can check out the new language feature, we first have to install TypeScript 2.0. At the moment of writing it didn’t appear yet as part of my Tools and Extensions Updates inside Visual Studio, so let’s go to the TypeScript website and download the code from there. Take the editor of your choice and install the required package. Enable Strict null checking in Visual Studio After installing TypeScript 2.0, strict null checking is not enabled out of the box. An extra compiler flag ( —strictNullChecks ) is required to switch to strict null check mode. To enable it in Visual Studio, you should unload your csproj file, edit it and add the following line to a propertygroup: <TypeScriptStrictNullChecks>True</...

Great announcement by Microsoft yesterday. They provided the first developer preview release of the new, simplified Azure management libraries for .NET. Thanks to a fluent interface-inspired method chains in combination with IntelliSense it delivers an easy to use experience. Here is an example: I don’t think it can become any easier… More information: The announcement: https://azure.microsoft.com/en-us/blog/simpler-azure-management-libraries-for-net/ The related github site: https://github.com/Azure/azure-sdk-for-net/tree/Fluent

This is a continuation of a previous post . Quick recap, I got an “ Unsupported Type encountered ” error when trying to send a message from an Orleans client to a silo. I tried a lot of other things (adding and removing the [ Serializable ] attribute, creating a custom serializer , …) before I landed at the real solution. When comparing our code with a sample I created using the Orleans template project in Visual Studio , I noticed that I had a specific NuGet package missing: <?xml version="1.0" encoding="utf-8"?> <packages>   <package id="Microsoft.Orleans.Core" version="1.2.4" targetFramework="net452" />   <package id="Microsoft.Orleans.OrleansCodeGenerator.Build" version="1.2.4" targetFramework="net452" /> </packages> Without this package doesn’t integrate in your build pipeline. Why is this important? Because behind the scenes Orleans is...

I’m currently working on a project where we are using Microsoft Orleans, an actor implementation optimized for Azure. Everything was working fine until we tried to add a web role with an Orleans client to interact with our Orleans silos through a Web API. However when we tried to send a message from the Web Api to the silo, following error message showed up inside the logs: !!!!!!!!!! Exception deserializing message body Exc level 0: System.Runtime.Serialization.SerializationException: Unsupported type 'Sample.Contracts.SampleMessage' encountered. Perhaps you need to mark it [Serializable] or define a custom serializer for it? at Orleans.Serialization.SerializationManager.DeserializeInner(Type expected, BinaryTokenStreamReader stream) at Orleans.Serialization.BuiltInTypes.DeserializeOrleansResponse(Type expected, BinaryTokenStreamReader stream) at Orleans.Serialization.SerializationManager.DeserializeInner(Type expected, BinaryTokenStreamReader stream) at Orleans.Serializat...

One of the great features of IIS is Failed Request Tracing . It offers you an easy configurable way to log all kind of information related to one or more specific error codes. This gives you deep insight into the IIS pipeline and is one of my last resorts in case something is going wrong on the webserver. The generated logs are large XML files that are hard to read and understand. Luckily in the same folder where your log files are generated(by default c:\inetpub\log\FailedReqLogFiles\W3SVC1) there should also be an XSLT file freb.xsl that transforms the XML into something that normal people could understand. Tip: In case the freb.xsl is missing, delete the folder that contains the log files and IIS will generate the folder again including the missing freb.xsl when the next failed request is logged.

Last week I had to investigate an issue in an old webservice that was still using basic authentication(on a not enforced HTTPS connection ). With basic authentication you have to send a Base64 encoded version of your username/password combination to the server(that explains immediatelly why using basic authentication over a HTTP connection is never a good idea). I had to the test the service but the only tool I had available on the server was Fiddler . So let’s start by creating the Base64 encoded version of our message: Open Fiddler Go to Tools –> TextWizard… Type your username password combination separated by a ‘:’, e.g. username:password Choose ToBase64 from the Transform list Copy the generated string Next step is to create our request: Go to the Composer tab Type “Authorization: Basic’’after the User-Agent string and add the generated string to the end. The result should look like this: Authorization: Basic dXNlcm5hbWU6cGFzc3dvc...

The default ASP.NET SessionStateModule is already partly asynchronous; it reads the request state asynchronous, but it doesn’t support async when reading/writing to the session store.  In the .NET Framework 4.6.2 release , Microsoft changed this by introducting a new interface named ISessionStateModule . Thanks to the async SessionState module it becomes possible to access the session storage providers(SQL Server, Redis,…) asynchronously. Async I/O operation helps release the thread more quickly than synchronous I/O operation, and ASP.NET can handle other requests. Here are the required steps to start using this module: Change your application to target .NET Framework 4.6.2 Download and install the Microsoft.AspNet.SessionState.SessionStateModule NuGet package. This will replace the default session state provider by the new async one. Download an async session state provider from NuGet. At the moment of writing I only could find an implementation for SQL Server , ...

When trying to build our Xamarin.Forms project on a VSTS hosted build server, our build failed first with the following error message: Error CS1703 Multiple assemblies with equivalent identity have been imported: ‘C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\MonoAndroid\v1.0\mscorlib.dll’ and ‘C:\WINDOWS\Microsoft.NET\Framework\v4.0.30319\mscorlib.dll’. Remove one of the duplicate references. On our local system it worked without any compiler errors. We tried the easiest solution first, following the advice as mentioned in the error message. We removed the mscorlib.dll from the references. After doing that, everything was working again. I hate it when the behavior differs between a local Visual Studio Build and the build server

A colleague contacted me to investigate a problem some of his customers had when opening an RDLC(local Reporting Services report) inside a ReportViewer control. Instead of a nice looking report, they got the following error message: An unexpected error occurred in Report Processing. Could not load file or assembly 'Microsoft.SqlServer.Types, Version=11.0.0.0, Culture=neutral, PublicKeyToken=89845dcd8080cc91' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040) Strange! We had no clue why this error appeared. I don’t see a reason why this DLL is needed. Anyway we solved it by downloading the assembly through NuGet( https://www.nuget.org/packages/Microsoft.SqlServer.Types/ ) and including it in the installation package. If anyone has a clue why this DLL is required, feel free to share! Remark: Even stranger was that we hadn’t this problem with a previous release.

Next step in my journey into Orleans land, was using ‘ Declarative Persistence ’. Sometimes you want the state inside your actors(grains in Orleans terminology) being persisted in some kind of permanent storage, so that it can survive a silo shutdown. Orleans provides a simple declarative model that makes this possible. Unfortunately while following the related tutorial , I got the following error message: [2016-10-04 07:19:17.848 GMT    11      ERROR   103104  Catalog 127.0.0.1:11111]        !!!!!!!!!! No storage providers found loading grain type Grains1.Manager No storage providers found loading grain type Grains1.Manager Exception = Orleans.Storage.BadProviderConfigException: No storage providers found loading grain type Grains1.Manager    at Orleans.Runtime.Catalog.SetupStorageProvider(ActivationData data)    at Orleans.Runtime.Catalog.CreateGrainIns...

I’m currently experimenting with Orleans and trying to compare it with my experiences using Akka.NET and the Azure Service Fabric actors. So far I like the experience although I encountered some issues in the beginning. I got my first problem when trying the “hello world” of actor model examples; https://dotnet.github.io/orleans/Tutorials/My-First-Orleans-Application.html . After following the tutorial, my Orleans host blew up with the following exception: ERROR starting Orleans silo name=[MyMachineName] Exception= Exc level 0: System.Net.Sockets.SocketException: An attempt was made to access a socket in a way forbidden by its access permissions at System.Net.Sockets.Socket.DoBind(EndPoint endPointSnapshot, SocketAddress socketAddress) at System.Net.Sockets.Socket.Bind(EndPoint localEP) at Orleans.Runtime.SocketManager.GetAcceptingSocketForEndpoint(IPEndPoint address) at Orleans.Runtime.Messaging.IncomingMessageAcceptor..ctor(MessageCenter ms...