Unity 3D The type or namespace name 'xxx' does not exist in the namespace 'xxx'

Unity3D 导入"Unity-Chan!" Model 后报错

error: CS0234 The type or namespace name ‘xxx’ does not exist in the namespace ‘xxx’ (are you missing an assembly reference?)

Unity 3D The type or namespace name 'xxx' does not exist in the namespace 'xxx'

原因不明,受同学启发,解决了问题,解决方式如下 :
File->Build Settings->Play Settings->然后如图
Unity 3D The type or namespace name 'xxx' does not exist in the namespace 'xxx'

解决完毕,如图 :
Unity 3D The type or namespace name 'xxx' does not exist in the namespace 'xxx'