c# - Why do I get the following error? Invalid variance modifier. Only interface and delegate type parameters can be specified as variant -

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 using system;  using system.collections.generic;  using system.linq;  using system.text;  namespace variance  {   class { }    class b : { }    class c<out t>  { }  class program {     static void main(string[] args)     {         var v = new c<b>();          ca(v);     }      static void ca(c<a> v) { }   } }

this offending line:

class c<out t>

as error message tells you, can't apply generic variance classes, interfaces , delegates. okay:

interface c<out t>

the above not.

for details, see creating variant generic interfaces


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