Angular *ngSwitchCase is not executing

I am new to Angular. I am using ngSwitch in my program but every time I run the program *ngSwitchDefault executes rather than *ngSwitchCase. Here is the code:

<select [(ngModel)]="selectedControl" class="form-control">
    <option *ngFor="let inputControl of inputArray; let i=index" 
    [value]="inputControl">{{inputArray[i]}}</option>                                  
</select>
<span [ngSwitch]="selectedControl">
    <span *ngSwitchCase="text">
    <p>text is selected</p>              
    </span>
    <span *ngSwitchCase="radio">
    <p>radio is selected</p>
    </span>        
    <span *ngSwitchDefault>
    <p>Default value</p>
    </span>
</span>

Wrap the *ngSwitchCase expressions into the '' to make them strings. The comparison will be used with ===, so it will compare string with string. In your case it is going to find a member with name radio or text and get their values, which are undefined.

<span [ngSwitch]="selectedControl">
    <span *ngSwitchCase="'text'">
    <!--                 ^----^ -->
    <p>text is selected</p>              
    </span>
    <span *ngSwitchCase="'radio'">
    <!--                 ^-----^ -->
    <p>radio is selected</p>
    </span>        
    <span *ngSwitchDefault>
    <p>Default value</p>
    </span>
</span>