Validation for select in template driven using angularjs 2

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I have form like below

<h1>Add user</h1>
<form #f="ngForm"
      novalidate
      (ngSubmit)="onSave(f.value)">
  <input
      type="text"
      name="name"
      [(ngModel)]="user.name"
      #name="ngModel"
      required="required"
      minlength="5">

    <span [hidden]="name.valid || (name.pristine && !f.submitted)" class="text-danger">
          Name is required (minimum 5 characters).
        </span>
     <select  name="application_name" [(ngModel)]="ProductName" (ngModelChange)="onSelectApplication()" required #ProductName="ngModel">
                              <option value="" infor-translate="select_application_name"></option>
                              <option *ngFor="let item of ProductName" [ngValue]="item">{{item.ProductName}}</option>
                          </select>
   <button type="submit" class="btn btn-default">Submit</button>
</form>

Could you please tell me that how to give error message for dropdown box

What I have tried:

I have tried

<span class="errorMessage" 
                              [hidden]="ProductName.selectedValue=='select_application_name' || (ProductName.pristine && !addAvailableApis.submitted)">
                            Required
                        </span>