如果您使用以下 ::ng-deepsnack-bar-container 为您的课程添加前缀，它似乎可以工作(请参阅 this 评论).所以你的组件 SCSS 文件应该是这样的:

It seems to work if you prefix your class with the following ::ng-deep snack-bar-container (see this comment). So your component SCSS file should look like this:

::ng-deep snack-bar-container.alert-red{
  padding: 20px;
  background-color: red;
  color: white;
}

WORKAROUND:见这里的帖子，看来你需要把样式放进去您的应用程序 styles.scss 文件，而不是您的组件 SCSS 文件.

WORKAROUND: See post here, it seems that you need to put the style in your applications styles.scss file and not in your components SCSS file.

检查这个 stackblitz，该样式在 styles.scss 中有效，但当您将其注释掉并将其保留在 app.component.scss 中时则无效.不确定这是错误还是预期行为.

Check this stackblitz, the style works in the styles.scss, but not when you comment it out and leave it in the app.component.scss. Not sure if this is a bug or intended behaviour.