如何在where语句后添加泛型参数？

Question

我有一个抽象类如下：

class BaseReturnType { }    
class DerivedReturnType : BaseReturnType { }    

abstract class BaseClass<T> where T : BaseReturnType    
{        
  public abstract T PolymorphicMethod();    
}    

class DerivedClass : BaseClass<DerivedReturnType>    
{
  public override DerivedReturnType PolymorphicMethod()        
  {            
    return new DerivedReturnType();        
  }    
}

因此，如果为Generic添加额外参数T2，我该如何对此进行extrac约束？

abstract class BaseClass<T, **T2**> where T : BaseReturnType ???  
    {        
      public abstract T PolymorphicMethod();    
    }   

Answer 1

abstract class BaseClass<T, **T2**> where T : BaseReturnType where T2 : BaseTypeForT2

    {        
      public abstract T PolymorphicMethod();    
    }

根据here。