<mat-slide-toggle  labelPosition = "before" *ngIf="element.Active==true" [checked]="true"  (change)="changeActive(element.IdCateg,element.Active)" >{{ t("Enable / Disable") }} ! </mat-slide-toggle>  

 <mat-slide-toggle  labelPosition = "before" *ngIf="element.Active==false" [checked]="false"  (change)="changeActive(element.IdCateg,element.Active)" >{{ t("Enable / Disable") }} ! </mat-slide-toggle>