title: ngFor not refreshing in Angular2 and keeps on adding elements
body: <p>I have a variable <code>var</code> as a drop down in my html.
  As my variable changes, A list is displayed for that particular value of <code>var</code>.
  Like :</p>
  
  <pre><code>&lt;ul *ngFor="let value in someArrayDependentOnvarInTheAboveDropdown"&gt;
      &lt;li&gt; {{value}} &lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p>Again as I change <code>var</code> in the dropdown, the array <code>someArrayDependentOnvarInTheAboveDropdown</code> is also changed in the function. But the previous <code>li</code> values are also shown in the html. 
  Like:</p>
  
  <pre><code>&lt;li&gt; Value1 from var1 &lt;/li&gt;
  &lt;li&gt; Value1 from var1 &lt;/li&gt;
  &lt;li&gt; Value1 from var2 &lt;/li&gt;
  &lt;li&gt; Value1 from var3 &lt;/li&gt;
  &lt;li&gt; Value1 from var3 &lt;/li&gt;
  ....
  </code></pre>
  
  <p>Please help in resolving this. Thanks in advance.</p>
  
  <p>This is the exact code snippet </p>
  
  <pre><code>changePlSelection(productLine) {
          console.log(productLine.product_line_name); 
          this.selectedProductLine = productLine;
  
          var position = 0;
          for(var i=0; i &lt; this.productLinesList.length; ++i) {
              if(productLine.product_line_id == this.productLinesList[i].product_line_id) {
                  position = i;
                  break;
              }
          }
  
          this.selectedProductApplicationsList = this.productApplicationsList[position];
  }
  </code></pre>
  
  <p>And the html code is :</p>
  
  <pre><code>&lt;ul&gt;
      &lt;li *ngFor="let productLine of productLinesList"&gt; 
          {{productLine.product_line_name}}
          &lt;input type="radio" 
                 name="radiogroup" 
                 [value]="productLine.product_line_id" 
                 (change)="changePlSelection(productLine)"&gt;
      &lt;/li&gt;
  &lt;/ul&gt;
  
  
  &lt;ul&gt;
      &lt;li id="list-of-pa" *ngFor="let productApplication of selectedProductApplicationsList"&gt; 
      {{productApplication.product_application_name}}    
      &lt;input type="radio" 
             name="radiogroup2" 
             [value]="productApplication.product_application_id" 
             (change)="changePaSelection(productApplication)"&gt;
       &lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>