c# - Declaring object of interface instead of implementation class -

this question has answer here:

• c# interfaces - what's point? 27 answers

i found code creates object of implementation class , assigning interface class variable:

myinterface obj=new myimplementationclass(); 

why dont use

 myimplementationclass obj=new myimplementationclass(); 

?

there may more 1 class implements myinterface. if use:

myinterface obj = new myimplementationclass(); 

you can do:

myinterface obj = new myotherimplementationclass(); 

but if use concrete implementation name, cannot (*):

// wouldn't work: myimplementationclass obj = new myotherimplementationclass(); 

and wouldn't able use following:

myinterface obj = new myinterface(); 

because don't know insantiate. should myinterfaceimplementation? should myotherinterfaceimplementation?

but there's technique called dependency injection. let's somehow bind specific implementation type. it, can following:

myinterface obj = dependencyinjectioncontainer.resolve<myinterface>(); 

take @ what dependency injection?.

(*) unless myotherimplementationclass inherits myimplementationclass.