angular7 with devextreme in visual studio 2017 not working

问题

I have setup angular project in vs2017 with angular cli template.

Now i want to use devextreme with angular, so according to official documentation i have installed npm install --save devextreme devextreme-angular.

But i have got erroe not installed in npm dependencies like below image:

so how to solve this. i have tried to restore packages, but it not works.

来源：https://stackoverflow.com/questions/54630743/angular7-with-devextreme-in-visual-studio-2017-not-working