从接口方法结果到整数的简单转换

Question

我有IBookRepository接口。该接口具有返回整数的方法CountAllBooks（）。 如果我在方法内接收类型对象的值

public object Convert(object value)

如果传递的对象是IBookRepository类型，为什么我不能将它的CountAllBooks结果转换为整数，如

public object Convert(object value)
{
   int c;
   if(value is IBookRepository)
   {
      c = (int)value.CountAllBooks();
   }
}

Answer 1

public object Convert(object value)
{ 
   int c;
   if(value is IBookRepository)
   {
      c = (int)((IBookRepository)value).CountAllBooks();
   }
   return c;
}

Answer 2

试试这个：

public object Convert(object value)
{
   int c;
   if(value is IBookRepository)
   {
      c = (int)(value as IBookRepository).CountAllBooks(); //casting "object" to "IBookRepository"
   }
}