如何在where語句後添加額外的泛型參數？

Question

我有一個抽象類，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();   
    }  
} 

所以，如果添加EXTA parrameter爲通用名爲T2我怎麼把爲Extrac制約對此有何看法？

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();  
    } 

按here。