Answers for "ERROR in src/app/app.module.ts(11,8): error TS2306: File 'D:/DevExtreme/DevExtreme_Demo/node_modules/@angular/material/index.d.ts' is not a module."

@angular/material/index.d.ts

It is changed in updated version of angular i think.
To resolve this issue you need to downgrade the angular/material version

Try to update the angular material (@angular/[email protected]) of this version.

npm uninstall -g @angular/material
npm cache clean --force

npm install -g @angular/material@7