c# - Determine datatype parameter for generic used in interface -

i struggling find elegant solution in determining data type in interface used generic parameter in abstract class.

abstract class:

public abstract class entity<t> {     /// <summary>     /// object identifier     /// </summary>     public t id { get; set; } } 

concrete class:

public class department: entity<int> {   // additional properties }  public class employee: entity<long> {   // additional properties } 

interface implementation:

public interface iservice<t1, t2>  t1 : entity<?>  t2 : entity<?> {   task transferemployeetodepartment(? departmentid, ? employeeid); } 

a solution problem send data type additional parameter personal , ocd reasons prefer not so. there way solve this?

agree dennis comment. according method name transfer concrete class employee concrete class department. there nothing generic here.
if want transfer these 2 entities code should this

public class department: entity<int> {   // additional properties }  public class employee: entity<long> {   // additional properties      public department transfertodepartment() {} //implementation here } 

if goal transfer entity entity remake yout interface following way

public interface iservice<t1, t2> {     task transferemployeetodepartment(entity<t1> entityfrom, entity<t2> entityto); } 

but if set of unrelated entities (like department , employee) doubt possible write generic code this