c# - Calling item methods on an array of different types -

my task simple: have create dynamic array (which means size can change during runtime) , fill (depends on user input, in runtime) objects of different types. moreover, should possible me access fields (and/or methods) of every object in array. obviously, fields different each type. simplified structure:

public class point {} public class righttriangle:point { public double sidea, sideb; } public class circle:point { public double radius; } public class cone:circle { public double radius, height; } 

so, see: classes inherit 1 base class. , know, these structure kind of illogical, that's not choice. so, want code work:

righttriangle rt1 = new righttriangle(); cone cn1 = new cone(); list<point> objs = new list<point>(); objs.add(rt1); sidea_tb.text = objs[0].sidea.tostring(); 

but doesn't. compiler says there no sidea in point. not work either:

public class point { public double sidea, sideb, radius, height; } public class righttriangle:point { public new double sidea, sideb; } public class circle:point { public new double radius; } public class cone:circle { public new double radius, height; } 

it seems values actual class (rt1, righttriangle) not override ones in point class, i've got this:

list<point> objs = new list<point>(); objs.add(rt1); // rt1 has fields 'sidea' = 4, 'sideb' = 5 sidea_tb.text = rt1.sidea.tostring(); // got 4, okay sidea_tb.text = objs[0].sidea.tostring(); // got 0, the? 

so, basically, need dynamic array of links, , want use links access objects fields , methods. also, know can write get/set functions in base class , override them in child classes, not seems beauty solution. in advance , please forget illiteracy (english isn't native).

you had (in theory):

public class point { public virtual double sidea, sideb, radius, height; } public class righttriangle:point { public override double sidea, sideb; } 

to make properties , methods overridable in derived classes have declared virtual in base class. overriding class has declare overriden property/method override.

in practice cannot make fields virtual, properties , methods can be. have change code follows:

public class point {      public virtual double sidea { get; set; }      public virtual double sideb { get; set; }     public virtual double radius { get; set; }     public virtual double height { get; set; } }  public class righttriangle:point {      public override double sidea { get; set; }     public override double sideb { get; set; } } 

however, should not bad design. more below.

so what's difference new?

when method overriden decided at runtime whether overridden or original implementation called.

so when method receives point argument, point instance might righttriangle or circle.

point p1 = new righttriangle(); point p2 = new circle(); 

in above example, both p1 , p2 points perspective of code uses p1 , p2. however, "underneath" instances of derived classes.

so solution, when acess p1.sidea example, the runtime "underneath" , check point is: righttriangle? check if there overridden implmentation of sidea , call one. circle? same check (which fail) , call original implmentation of sidea.

the new qualifier else. not override method, create new 1 (with same name), handled differently at compile time.

so solution, compiler sees created righttriangle , stored in variable of type point. when access p1.sidea example, compiler compile access in such way reads sidea base class, since instance variable dealing has base type.

if still want access new implementation, code using p1 has cast correct derived type righttriangle:

var w = ((righttriangle)p1).sidea; // gets correct value. 

so what's problem?

as may have noticed now, using new not solution. code uses kinds of points has know whether specific derivate of point implements field new or not. has know, when receives point instance kind of instance acutally underneath. lead lots of elaborate if-else statements check kind of point p1 being dealt , run appropriate behvaiour.

using virtual , override alleviates last problem, if base class implements all methods , properties derived class implements. kind of insane. tried , i'm sure noticed on way doesn't make sense give point sidea , sideb and radius. how point ever implement properties meaningfully? , cannot make them abstract either, because circle had implement sidea , on.

so how solve in better way?

think want whith differnet point instances. collect them in list reason: have in common. iterate on list doing each 1 of them specific reason well. trying exactly? can describe in abstract way?

maybe getting side lengths , radiuses calculate area? give point virtual method getarea() , override in each derived class. method getarea() makes sense on derived types, although implemented differently in each 1 of them.

you make getarea() abstract method instead of virtual one. means not implemented in base class @ , derived types forced implement on own.

maybe don't want handle points in list righttriangles only? code doing should receive righttriangles:

public void handlerighttriangles(ienumerable<righttriangle> rts) {     // can work sidea , sideb directly here, because know got triangles. } 

call with:

// using system.linq; handlerighttriangles(objs.oftype<righttriangle>());