c# - Can't use an instance variable of non-generic class inheriting from a generic class with specified type -

i created classes these:

abstract class aclass1<t> {     // code here }  class class2 : aclass1<int> {     // code here }  class class3 : aclass1<float> {     // code here }  class class4<t> : aclass1<t> {     // code here } 

so far works. in class i'd have:

... aclass1<t> variable; 

and depending on specific needs set variable either:

variable = new class2(); 

or

variable = new class3(); 

or sometimes:

variable = new class4<t>(); 

this produces compile error no possible cast or else tried. @ moment changed inheriting classes generic like:

class class2<t> : aclass1<t> {     // code here } 

but doesn't feel right, because there no generic methods or there.

the question right way it, why, , why can't using original way?

by way .net 2.0 i'm doing inside unity3d.

to more clear:

i have specific cases e.g. int type want handle specifically, there other i'd have generic class for. created subclasses specifcally handle types , have generic subclass use when there no specific implementation type. when create specific class type should not generic handles 1 type.

the compiler trying ensuring don't perform assignments aren't guaranteed work. isn't legal:

void foo<t>() {   ...   if (typeof(t) == typeof(int)) {     aclass1<t> variable = new class2();   }   ... } 

and that's because class2 compatible aclass1<int> -- if don't know t is, can't in general it's compatible aclass1<t>. in code above, it's certainty conversion possible, compiler isn't sophisticated enough determine code safe -- in general, without if, wouldn't be. casting doesn't work either, because there no conversion class2 aclass1<t> arbitrary t.

to make work, have forego compile-time type checking , force runtime conversion -- it's legal cast , object @ compile time:

    aclass1<t> variable = (aclass1<t>) (object) new class2(); 

if wrong, code fail @ runtime invalidcastexception.

this approach dubious because raises question of why using generics (a compile-time type feature) , circumventing them in actual code. code has reviewed see if appropriate solution. possible alternatives introducing non-generic base class, using containment generic types, or not using generics (if you're using float , int, generic base class adding anything?)