Angular Form Validation error : form is undefined - forms

Question

I am trying to validate my data for a student object with Angular Form Validation, but when I want to use or print for example, the serialNumber of a student it gives me this error: Cannot read property 'serialNumber' of undefined.
Here is the code:
<div *ngIf="student">
<div class=container>
<h2>Student {{student.name}} details</h2>
<form name="studentForm" (ngSubmit)="save()">
<!--<div ng-class="{ 'has-error' : studentForm.serialNumber.$invalid && !studentForm.serialNumber.t">-->
<label>Serial number: {{student.serialNumber}} </label>
<input type="text" name="serialNumber" class="form-control" ng-model="student.serialNumber" required>
<div ng-messages="studentForm.serialNumber.$error">
{{studentForm.serialNumber}}
<p ng-message="required">Your name is required!</p>
</div>
<!--</div>-->
<div>
<label>Name: {{student.name}}</label>
<input ng-model="student.name" placeholder="name">
</div>
<div>
<label>Group number: {{student.groupNumber}}</label>
<input ng-model="student.groupNumber" placeholder="groupNumber">
</div>
<button (click)="goBack()">Back</button>
<button (click)="save()">Save</button>
</form>
</div>
</div>

Answer 1

The ng-messages and ng-model attribute directives do not exist in Angular 2+. I would recommend reading into Angular Forms, ReactiveForms, and Template Syntax.
If you would like to dual data-bind the input values, you can do so with the following syntax: [(ngModel)]="student.serialNumber". However, in Angular 2+, there are usually better ways of getting values other than explicitly data-binding.

Answer 2

Angular Form Validation template Driven Model
onSubmit(form : NgForm) {
console.log(form);
}
<form #form="ngForm" (ngSubmit)="onSubmit(form)"
[ngClass]="{'was-validated': form.invalid && (form.dirty || form.touched)}">
<div class="" ngModelGroup="User">
<h2 class="text-center">Registration page</h2>
<br />
<div class="form-group">
<input type="text" class="form-control" placeholder="First Name" name="firstname" required
ngModel #firstname="ngModel">
<span class="help-bpx" *ngIf="firstname.touched && !firstname.valid ">Please enter the
firstname</span>
</div>
<div class="form-group">
<input type="text" class="form-control" placeholder="Last Name" name="lastname" required ngModel
#lastname="ngModel">
<span class="help-bpx" *ngIf="lastname.touched && !lastname.valid ">Please enter the
lastname</span>
</div>
<div class="form-group">
<input type="email" class="form-control" id="email" placeholder="Email" name="email" email
required ngModel #email="ngModel">
<span class="help-bpx" *ngIf="email.touched && !email.valid ">Please enter the Email
Value</span>
</div>
<div class="form-group">
<div class="custom-file">
<input type="file" class="custom-file-input" id="customFile" required ngModel name="file" #file="ngModel">
<label class="custom-file-label" for="customFile">Choose file</label>
</div>
</div>
<br />
<div class="align-center">
<button type="submit" class="btn btn-primary" [disabled]="!form.valid">Register</button>
</div>
</div>
</form>