您似乎缺少转换器:

internal class AnimalConverter : ExpandableObjectConverter {

  public override object ConvertTo(ITypeDescriptorContext context, 
                                   CultureInfo culture, 
                                   object value,
                                   Type destinationType) {

    if (destinationType == typeof(string) && value is Animal) {
      Animal a = (Animal)value;
      return a.ToString();
    }
    return base.ConvertTo(context, culture, value, destinationType);
  }
}

然后装饰你的动物:

[TypeConverter(typeof(AnimalConverter))]
public class Animal {...}

发现这个代码项目 自定义显示PropertyGrid 中的集合数据很有帮助.

Found this Code Project Customized display of collection data in a PropertyGrid helpful.