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Access a property using reflection

Cum putem face get/set la o proprietate prin intermediul la reflection. Odata ce avem tipul obiectului care contine proprietate, este de ajuns sa apelam InvokeMember si sa specificam numele proprietatii.
private TReturn GetProperty<TReturn>(object obj, string propertyName)
{
return (TReturn) obj.GetType().InvokeMember(
propertyName,
BindingFlags.GetProperty,
null,
obj,
null);
}

private void SetProperty(object obj, string propertyName, object value)
{
obj.GetType().InvokeMember(
propertyName,
BindingFlags.SetProperty,
null,
obj,
new object[] { value });
}
BindingsFlags se poate seta printr-un OR logic, in functie de proprietatea cu care lucram( publica, privata, statica, etc). De exemplu, pentru o proprietate publica si care nu este statica putem sa avem urmatorul apel:
 obj.GetType().InvokeMember(
propertyName,
BindingFlags.Instance | BindingFlags.Public | BindingFlags.SetProperty,
Type.DefaultBinder,
obj,
new object[] { value });
O alta modalitate de a lucra cu proprietati este sa obtim o instanta la PropertyInfo pentru proprietatea noastra, iar apoi sa facem get/set pe aceasta in felul urmator:
PropertyInfo propertyInfo = obj.GetType().GetProperty(propertyName);
propertyInfo.SetValue(obj, value, null);
Nu trebuie sa uitam ca numele la proprietate este case-sensitive.
Am incercat sa compar accesul direct la o proprietate cu cel prin reflection pentru 100.000.000 de accesari. Accesul proprietatilor prin reflection este cu circa 150 de ori mai lent decat prin accesul direct a unei proprietati. Per secunda, am avut circa ~145.000.000 de iteratii pe secunda pentru accesul direct in comparatie cu circa ~940.000.000 de iteratii pe secunde pentru accesul prin reflection.
Dar codul care folosea reflection nu a fost deloc optimizat. O sa revin cu un post in care o sa facem o optimizare a codului care foloseste reflection.
Enjoy!

Comments

  1. Daca un anume property e accesat de mai multe ori, poate ar merita vazut daca e mai performant sa folosesti Expression.Property(..) si sa cache-uiesti rezultatul..

    ReplyDelete
  2. Poate vreti sa va uitati la
    https://nuget.org/packages/Hydrate

    ReplyDelete
  3. Nu prea am înțeles, de ce e nevoie să folosesti BindingFlags.Public?

    ReplyDelete
  4. Prin intermediul la BindingFlag se setaza "locatia" unde se cauta membrul dat. De exemplu se foloseste Public, cand membrul este public. Daca acesta ar fi privat atunci ar fi nevoie sa se foloseasca BindingFlag.NonPublic. Daca membrul este static atunci se foloseste BindingFlag.Static. De multe ori este nevoie sa foloseste mai multe valori folosing un OR logic('|').

    ReplyDelete
  5. Sunt curios dacă poți ignora modificatorii de acces în felul ăsta, setând valori pentru o proprietate privată sau protected chiar dacă ești afară din linia de moștenire.

    ReplyDelete
  6. Prin reflection poti sa accesezi orice field privat. Uitate peste urmatorul link si vezi ce combinatii poti sa faci.
    http://msdn.microsoft.com/en-us/library/system.reflection.bindingflags.aspx

    ReplyDelete
  7. Dar poți și seta valori pe un field privat?

    ReplyDelete

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