CSS 编辑在谷歌浏览器控制台中工作，但在样式表中不工作

Question

I am trying to edit a form in Ionic 4. I can target HTML elements in chrome, however when I try to use these edits in the CSS within the app, it does not work.

When I add a style to the Element using chrome, it works like shown below.

I have tried to add these properties in the style sheet such as this

ion-item.div.item-native {
    background-color: blue !important;
}

div.item-native {
    background-color: blue !important;
}

.item-native {
    background-color: blue !important;
}

but it the result is this, which is not what I want.

How come the CSS is not working?

this is the HTML of form

<form class="form" [formGroup]="validations_form" (ngSubmit)="tryRegister(validations_form.value)">
<ion-item id ="item-native">
      <ion-label id ="item-native" position="floating" color="primary">Email</ion-label>
      <ion-input id ="item-native" type="text" formControlName="email"></ion-input>
    </ion-item >
    <div class="validation-errors">
      <ng-container *ngFor="let validation of validation_messages.email">
        <div class="error-message" *ngIf="validations_form.get('email').hasError(validation.type) && (validations_form.get('email').dirty || validations_form.get('email').touched)">
          {{ validation.message }}
        </div>
      </ng-container>
    </div>
    <ion-item>
      <ion-label position="floating" color="primary">Password</ion-label>
      <ion-input type="password" formControlName="password"></ion-input>
    </ion-item>
    <div class="validation-errors">
      <ng-container *ngFor="let validation of validation_messages.password">
        <div class="error-message" *ngIf="validations_form.get('password').hasError(validation.type) && (validations_form.get('password').dirty || validations_form.get('password').touched)">
          {{ validation.message }}
        </div>
      </ng-container>
    </div>
    <ion-button class="submit-btn" expand="block" type="submit" [disabled]="!validations_form.valid">Register</ion-button>
    <label class="error-message">{{errorMessage}}</label>
    <label class="success-message">{{successMessage}}</label>
  </form>

Answer 1

Remove dot for div element and Stop your running code and restart it will Work...!!

Wrong CSS

ion-item.div.item-native {
    background-color: blue !important;
}

Right CSS

ion-item div.item-native {
    background-color: blue !important;
}