title: How to fix the error “Could not find Angular Material core theme” in Angular 2?
body: <p>I am practically new in Angular2 and inherited the project with Angular 2 frontend.  After switching to the new Angular 4.0 on console I see the error:</p>
  
  <p>"compatibility.ts:221 Could not find Angular Material core theme. Most Material components may not work as expected. For more info refer to the theming guide: <a href="https://material.angular.io/guide/theming" rel="noreferrer">https://material.angular.io/guide/theming</a>"</p>
  
  <p>The mdb.min.css is in the app/assets/css folder.  The specification in package.json shows the following:</p>
  
  <pre><code>"@angular/common": "^4.0.0",
  "@angular/compiler": "^4.0.0",
  "@angular/core": "^4.0.0",
  ...
  "angular-bootstrap-md": "*"
  </code></pre>
  
  <p>How to fix the error?</p>