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;
if(entity==null)
{
//do something.
}else
{
...
}

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.

Comments

Windows Docker Containers can make WIN32 API calls, use COM and ASP.NET WebForms

After the last post , I received two interesting questions related to Docker and Windows. People were interested if we do Win32 API calls from a Docker container and if there is support for COM. WIN32 Support To test calls to WIN32 API, let’s try to populate SYSTEM_INFO class. [StructLayout(LayoutKind.Sequential)] public struct SYSTEM_INFO { public uint dwOemId; public uint dwPageSize; public uint lpMinimumApplicationAddress; public uint lpMaximumApplicationAddress; public uint dwActiveProcessorMask; public uint dwNumberOfProcessors; public uint dwProcessorType; public uint dwAllocationGranularity; public uint dwProcessorLevel; public uint dwProcessorRevision; } ... [DllImport("kernel32")] static extern void GetSystemInfo(ref SYSTEM_INFO pSI); ... SYSTEM_INFO pSI = new SYSTEM_INFO(...

How to audit an Azure Cosmos DB

In this post, we will talk about how we can audit an Azure Cosmos DB database. Before jumping into the problem let us define the business requirement: As an Administrator I want to be able to audit all changes that were done to specific collection inside my Azure Cosmos DB. The requirement is simple, but can be a little tricky to implement fully. First of all when you are using Azure Cosmos DB or any other storage solution there are 99% odds that you’ll have more than one system that writes data to it. This means that you have or not have control on the systems that are doing any create/update/delete operations. Solution 1: Diagnostic Logs Cosmos DB allows us activate diagnostics logs and stream the output a storage account for achieving to other systems like Event Hub or Log Analytics. This would allow us to have information related to who, when, what, response code and how the access operation to our Cosmos DB was done. Beside this there is a field that specifies what was th...

Cloud Myths: Cloud is Cheaper (Pill 1 of 5 / Cloud Pills)

Cloud Myths: Cloud is Cheaper (Pill 1 of 5 / Cloud Pills) The idea that moving to the cloud reduces the costs is a common misconception. The cloud infrastructure provides flexibility, scalability, and better CAPEX, but it does not guarantee lower costs without proper optimisation and management of the cloud services and infrastructure. Idle and unused resources, overprovisioning, oversize databases, and unnecessary data transfer can increase running costs. The regional pricing mode, multi-cloud complexity, and cost variety add extra complexity to the cost function. Cloud adoption without a cost governance strategy can result in unexpected expenses. Improper usage, combined with a pay-as-you-go model, can result in a nightmare for business stakeholders who cannot track and manage the monthly costs. Cloud-native services such as AI services, managed databases, and analytics platforms are powerful, provide out-of-the-shelve capabilities, and increase business agility and innovation. H...

Cloud as a Story - Vunvulea Radu

Search This Blog