change kendo grid row color conditionally using Angular ngClass or ngStyle does not work

Im using a Kendo detailed view Grid,in one my detail view data there is row which i want to be highlighted if the value meets my condition,i tried the following but i cant achieve it
here is my main grid component,

  <div *kendoGridDetailTemplate="let dataSource">
  <app-category-details>
  </app-category-details>
   </div>

app-category-detail is the detail component which is :

 template: `
      <kendo-grid
      [data]="dataSource"      
      scrollable="none"
      [navigable]="true"
      kendoGridFocusable>
     <kendo-grid-column field="deviceIP" title="Device IP">
     </kendo-grid-column>
     <kendo-grid-column field="comments" title="Comments"  [ngClass]="dataSource==='VPN Gateway' ? 'positive':'positive'" >
     </kendo-grid-column>
     </kendo-grid>

my condition is dataSource===’VPN Gateway’ but this code does not give any error and does not change anything also, seems i can’t use dataSource directly there,and if i use dataSource.comments it gives me the error that cant get the comments value of unknown.positive is a css class to change back ground.

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