Selection is enabled by setting selectionMode to one of possible values: single or multiple. In the single mode, a single TreeNode is expected as the value of the selection property. In the multiple mode, an array is expected. For example:

<p-organizationChart [value]="data"
  selectionMode="single" [(selection)]="selectedNode">
</p-organizationChart>

The organization chart supports two events:

Let's extend the previous developed organization chart as shown here:

<p-organizationChart [value]="data" styleClass="company"
  selectionMode="single" [(selection)]="selectedNode"
  (onNodeSelect)="onNodeSelect($event)">
  ...
</p-organizationChart>

In the demo application on GitHub, we defined a VCard interface representing a person's VCard:

export interface VCard {
  id: string;
  fullName: string;
  birthday: string;
  address: string;
  email: string;
}

All VCard instances are lazily fetched in the onNodeSelect callback. After that, a VCard to the clicked person (node) is shown in the PrimeNG dialog:

display: boolean = false;
selectedVCard: VCard;
private availableVCards: VCard[];

onNodeSelect(event: any) {
  if (this.availableVCards == null) {
    this.vcardService.getVCards().subscribe(
      (vcards: VCard[]) => {
        this.availableVCards = vcards;
        this.showInfo(event);
      });
  } else {
    this.showInfo(event);
  }
}

private showInfo(event: any) {
  this.selectedVCard = null;

  this.availableVCards.some((element: VCard) => {
    if (event.node.data && element.id === event.node.data.id) {
      this.selectedVCard = element;
      return true;
    }
  });

  if (this.selectedVCard) {
    // show VCard in dialog
    this.display = true;
  } else {
    // show node label in growl
    this.msgs = [];
    this.msgs.push({severity: 'Label', summary: event.node.label});
  }
}

The dialog itself looks like the following:

<p-dialog header="VCard" [(visible)]="display"
 modal="modal" width="320" [responsive]="true">
  <i class="fa fa-address-card-o"></i>
  <ul style="padding: 0.2em 0.8em;">
    <li>Full name: {{selectedVCard?.fullName}}</li>
    <li>Birthday: {{selectedVCard?.birthday}}</li>
    <li>Address: {{selectedVCard?.address}}</li>
    <li>E-mail: {{selectedVCard?.email}}</li>
  </ul>
</p-dialog>

The result is truly amazing: