title: Angular subscribe won't update when data changes
body: <p>I have a subscribe in typescript that pulls locations from my own ASP.NET database. However, they only pull the data once, but the locations should be updated live. How do I get my Observable to automatically update?</p>
  
  <p>I've tried to use ChangeDetectorRef, but it didn't solve the issue (neither <em>.MarkForCheck()</em> or <em>.DetectChanges()</em>).</p>
  
  <pre><code>getLocations(){
          console.log("Get them all!"); 
          this.API.getAllLocations().subscribe(result =&gt;{
              this.locations = result;
              console.log(this.locations);
              this.addLocationMarkers();
              this.ref.markForCheck();
          });
  }
  
  getAllLocations(): Observable&lt;Location[]&gt; {
      return this._http.get&lt;Location[]&gt;(this.url + "location/", this.headers);
  }
  </code></pre>
  
  <p>I can clearly see that <em>console.log(this.locations)</em> is only called once in my browser. Why isn't it called when the underlying data changes in the database?</p>