Added dropdown menu

src/app/main/main-center/main-center.component.html

@@ -13,4 +13,4 @@
 
 <ng-template #noPdf>
     <h1 class="ml-4 mt-4 text-danger">PDF not found</h1>
-</ng-template>
+</ng-template>

src/app/main/tree/tree.component.html

@@ -1,7 +1,25 @@
-<p-tree [value]="filesTree" selectionMode="single" (onNodeSelect)="nodeSelect($event)">
-    <ng-template let-node pTemplate="default">
-        <div class="tree">
-            <div class="flex-fill">{{ node.label }}</div>
-        </div>
-    </ng-template>
-</p-tree>
+<h2 class="ml-2">Select XA: </h2>
+
+<ng-container *ngIf="selectedXA == ''">
+    <h4 class="ml-2">Please select a model</h4>
+</ng-container>
+
+<select class="ml-2" ng-model="selectedXA" (change)="selectOptionHandler($event)">
+    <option value="">none</option>
+    <option value="uconn">UConn</option>
+    <option value="test">Test</option>
+</select>
+
+<ng-container *ngIf="selectedXA == 'test'">
+    <p class="ml-2">No information is available for selected model</p>
+</ng-container>
+
+<ng-container *ngIf="selectedXA == 'uconn'">
+    <p-tree [value]="filesTree" selectionMode="single" (onNodeSelect)="nodeSelect($event)">
+        <ng-template let-node pTemplate="default">
+            <div class="tree">
+                <div class="flex-fill">{{ node.label }}</div>
+            </div>
+        </ng-template>
+    </p-tree>
+</ng-container>

src/app/main/tree/tree.component.ts

@@ -12,6 +12,12 @@ export class TreeComponent implements OnInit {
 
   filesTree: TreeNode[];
 
+  selectedXA = '';
+
+  selectOptionHandler(event: any) {
+    this.selectedXA = event.target.value;
+  }
+
   constructor(
     private treeService: TreeService,
     private nodeService: NodeService