c# - Can I use generics to change a subclass' method signature? -

i need perform operation on subclass , return result:

public interface ientity { }  public abstract class entity : ientity {   public abstract ientity dostuff(ientity e1, ientity e2, ientity e3); }  public class customer : entity {   public override ientity dostuff(ientity e1, ientity e2, ientity e3) {    // <-- yuck   var customer1 = e1 customer;                                          // <-- yuck   var customer2 = e2 customer;                                          // <-- yuck   var customer3 = e3 customer;                                          // <-- yuck   // stuff   return foo;   } } 

i want avoid subclass' method signature, , associated typecasting.

so prefer this:

public override customer dostuff(customer c1, customer c2, customer c3) {   // stuff   return foo;   } 

how use type system accomplish that?

edit: i changed name of method compare dostuff, reiterate operation irrelevant. i'm not trying compare. want change types. how do that?

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many have said change design, cannot do. have solution, i've included below, , works. if have better way accomplish this, without criticising design (which not point), please let me know. everyone's contribution though.

this works. self-referencing generics make head hurt.

public interface ientity { }  public abstract class entity<tentity> : ientity tentity : ientity {   public abstract tentity dostuff(tentity e1, tentity e2, tentity e3); }  public class customer : entity<customer> {   public override customer dostuff(customer c1, customer c2, customer c3) {     // stuff     return foo;   } } 

is solution, or there gotchas in there that'll give me problems?

is there better solution?