dnet-applications/frontends/dnet-is-application/src/app/resources/content-dialog.html

<form [formGroup]="contentForm" (ngSubmit)="onSubmit()">

  <h1 mat-dialog-title>Edit content</h1>

  <div mat-dialog-content>

    <mat-form-field appearance="fill" floatLabel="always" style="width: 100%;">
      <mat-label>ID</mat-label>
      <input matInput readonly value="{{data.id}}"/>
    </mat-form-field>

    <mat-form-field appearance="fill" floatLabel="always" style="width: 100%;">
      <mat-label>Content ({{data.contentType}})</mat-label>
      <textarea matInput formControlName="content" required rows="16" style="font-size: 0.8em;"></textarea>
      <mat-error *ngIf="contentForm.get('content')?.invalid">This field is <strong>required</strong></mat-error>
    </mat-form-field>
  </div>

  <div mat-dialog-actions>
    <button mat-stroked-button color="primary" type="submit" [disabled]="!contentForm.valid">Submit</button>
    <button mat-stroked-button color="primary" mat-dialog-close>Close</button>
    <mat-error *ngIf="contentForm.errors?.['serverError']">
      {{ contentForm.errors?.['serverError'] }}
    </mat-error>
  </div>

</form>