Interface Step 1 export interface ITechnologies { technology ?: chkTechnology [], checkboxSlectedValues ?: string } export interface chkTechnology { name : string , isChecked : boolean , lable : string , cssClass ?: any } .tsx file Step 2 import { Label } from 'office-ui-fabric-react/lib/Label' import { Checkbox } from 'office-ui-fabric-react/lib/Checkbox' ; import { ITechnologies , chkTechnology } from './ICheckBoxControlstates' Step 3 public constructor ( prop : ICheckBoxControlProps , any ) { super ( prop ); this . state = { checkboxSlectedValues : "" , technology : [ { lable : "Sharepoint" , name : "Sharepoint" , isChecked : false , cssClass : styles . chkControl }, { lable : "SPFx" , name : "SPFx" , isChecked