title: Value must be an array in multiple-selection mode in angular material mat-select
body: <p>I am using angular material mat-select component.</p>
  
  <pre><code>        &lt;mat-table [dataSource]="dataSource" class="mat-elevation-z8" matSort &gt;
  
                &lt;ng-container matColumnDef="sensitive"&gt;
                  &lt;mat-header-cell class="table-header header-p" *matHeaderCellDef&gt; &lt;b&gt;sensitive&lt;/b&gt; &lt;/mat-header-cell&gt;
                  &lt;mat-cell class="table-content context-position "  *matCellDef="let element"  &gt;
                    &lt;mat-select placeholder="sensitive"  multiple [(ngModel)]="element.sensitive" &gt;
                      &lt;mat-option *ngFor="let type of sensitiveList" [value]="type"&gt;{{type}}&lt;/mat-option&gt;
                    &lt;/mat-select&gt;
                  &lt;/mat-cell&gt;
                &lt;/ng-container&gt;
  
                &lt;mat-header-row class="table-header-row" *matHeaderRowDef="displayedColumns"&gt;&lt;/mat-header-row&gt;
                &lt;mat-row  [ngClass]="((i%2) == 1) ? 'table-content-row-single' : 'table-content-row-double'"  *matRowDef="let row; columns: displayedColumns;"&gt;&lt;/mat-row&gt;
          &lt;/mat-table&gt;
  </code></pre>
  
  <p>typescript
           sensitiveList : string[] = [ 'none', 'sensitive'];
           for(var i=0;i
  
  <p>why running the code gives me an error</p>
  
  <pre><code>Value must be an array in multiple-selection mode
  </code></pre>