我找到了解决方案，谢谢大家的答复.

I found the solution, Thanks all for reply.

category = (Categoies)AutoMapper.Mapper.Map(viewModel, category, typeof(CategoriesViewModel), typeof(Categoies));

但是，我已经不知道原因了.我无法完全理解.

But, I have already dont know the reason. I cant understand fully.