Skip to main content

Cast using AS keyword

Cînd dorești să faci un cast .NET iți oferă mai multe posibilități. Astăzi o să vorbim despre doua dintre ele, varianta clasica, folosind paranteze și cea folosind AS.
Mod de folosire:
IEntity entity=(IEntity)student;
IEntity entity=student as IEntity;
//do something.
Cînd se foloseste AS trebuie sa fim atenți in cazul in care cast-ul nu se poate face, moment in care variabila o sa aibe valoarea NULL. In general o sa fie nevoie sa se verifice daca cast-ul s-a putut face sau nu.In cele mai multe scenarii din lumea reala, o sa avem nevoie ca o exceptie sa fie aruncata, deoarece este posibil ca un alt tip sau assembly sa fi fost folosit. Sunt momente cand AS isi gaseste locul. In metodele private unde s-a facut deja o validare a datelor folosite sau avem certitudinea ca datele primite sunt asa cum ne asteptam.
Dar AS mai ascunde ceva, o problema de performanta. Mecanismul care sta in spate nu este magic deloc. In spate se face o verificare simpla, dacă conversia se poate face sau nu, iar in cazul in care acesta nu se poate face se returnează null. Ceva ce noi am putea implementa in felul urmator:
IEntity=entity is IEntity?(IEntity)entity:null;
Din cauza la acesta verificare in plus AS este mai lent cu circa 40%. Dar asta nu ii un motiv să nu îl folosim in aplicațiile de zi cu zi. Probleme de performanta nu ar trebuii să apară in general, dar este bine să se tina cont de acest lucru cînd se scrie o bucata de cod unde performanta este critica.
Pentru teste am folosit următorul cod( click pe imagine pentru a vedea codul):
Părerea mea personala este să nu folosiți AS, doar in cazuri speciale unde acesta își are rostul. Poate ca pare mai ușor de scris ca un cast cu AS, dar acesta poate să cauzeze erori ciudate cauzate de valoarea null, mai ales cînd cast-ul se face într-un loc, iar variabila este apoi folosita într-o alta metoda sau este trimisa mai departe.


Popular posts from this blog

How to check in AngularJS if a service was register or not

There are cases when you need to check in a service or a controller was register in AngularJS.
For example a valid use case is when you have the same implementation running on multiple application. In this case, you may want to intercept the HTTP provider and add a custom step there. This step don’t needs to run on all the application, only in the one where the service exist and register.
A solution for this case would be to have a flag in the configuration that specify this. In the core you would have an IF that would check the value of this flag.
Another solution is to check if a specific service was register in AngularJS or not. If the service was register that you would execute your own logic.
To check if a service was register or not in AngularJS container you need to call the ‘has’ method of ‘inhector’. It will return TRUE if the service was register.
if ($injector.has('httpInterceptorService')) { $httpProvider.interceptors.push('httpInterceptorService&#…

ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded

Today blog post will be started with the following error when running DB tests on the CI machine:
threw exception: System.InvalidOperationException: The Entity Framework provider type 'System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer' registered in the application config file for the ADO.NET provider with invariant name 'System.Data.SqlClient' could not be loaded. Make sure that the assembly-qualified name is used and that the assembly is available to the running application. See for more information. at System.Data.Entity.Infrastructure.DependencyResolution.ProviderServicesFactory.GetInstance(String providerTypeName, String providerInvariantName) This error happened only on the Continuous Integration machine. On the devs machines, everything has fine. The classic problem – on my machine it’s working. The CI has the following configuration:

TeamCity.NET 4.51EF 6.0.2VS2013
It seems that there …

Run native .NET application in Docker (.NET Framework 4.6.2)

The main scope of this post is to see how we can run a legacy application written in .NET Framework in Docker.

First of all, let’s define what is a legacy application in our context. By a legacy application we understand an application that runs .NET Framework 3.5 or higher in a production environment where we don’t have any more the people or documentation that would help us to understand what is happening behind the scene.
In this scenarios, you might want to migrate the current solution from a standard environment to Docker. There are many advantages for such a migration, like:

Continuous DeploymentTestingIsolationSecurity at container levelVersioning ControlEnvironment Standardization
Until now, we didn’t had the possibility to run a .NET application in Docker. With .NET Core, there was support for .NET Core in Docker, but migration from a full .NET framework to .NET Core can be costly and even impossible. Not only because of lack of features, but also because once you…