c# - Create a custom user collection of collections -

i need create generic collection of generic collections, should contain generic class. i've tried hard, haven't found answers.this how realizated collection looks like: https://github.com/infatum/pmc-data-model/blob/master/wtf/position.cs collection of position of generic class point. need create indexed collection of positions called matrix, indexed collection of matrix called container , indexed collection of containers, named containers. please, me!

public class matrix<t> : icollection<t> t : position<t> {     protected arraylist matrix;     protected bool isreadonly;      public matrix()     {         matrix = new arraylist();     } // ... } 

the trouble : type 't' cannot used type parameter 't' in generic type or method 'position'. there no implicit reference conversion 't' 'wtf.point'

this task, given me: https://docs.google.com/document/d/1zyxxajrh0oynluufy0ht6zuazisiece73cga4qordlc/edit#heading=h.nwbuqfwpq3gk

your type constraint on t recursive - don't think want be. (and neither compiler: constraint enforces t sort of position<t>. means position<t> position<position<t>> - violates type constraint on generic argument of position, expects wtf.point instead of position)

solution:

public class matrix<t> : icollection<position<t>> 

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but let me elaborate little more: in sense, want like

public class matrix<t> : icollection<t> t : position<u> 

so there no more recursion. want t "some kind of position". have new problem: u (let's call "element-type") come from? should use that generic type argument of matrix:

public class matrix<u> : icollection<t> t : position<u> 

now, constraint can collapsed directly interface type, i.e. icollection<position<u>> giving solution gave above (modulo names).