title: Xamarin.Forms setting IsEnable to true not working
body: <p>I am using Xamarin.Forms and I am trying to use disable a button and then enable it when the button action is finished, when I disable it, the button does in fact become disabled, but when I enable it, its still disabled, what am I doing wrong? Here is my full method:</p>
  
  <pre><code>private void OnCameraScan(object sender, EventArgs e)
  {
      ScanLicence.IsEnabled = false;
  
      var barcodeScanView = new ZXing.Net.Mobile.Forms.ZXingScannerView
      {
          HeightRequest = 200
      };
  
      ScannerWrapper.HeightRequest = 200;
      ScannerWrapper.IsVisible = true;
  
  
      var options = new MobileBarcodeScanningOptions
      {
          TryHarder = true,
          CameraResolutionSelector = HandleCameraResolutionSelectorDelegate,
          PossibleFormats = new List&lt;BarcodeFormat&gt; { BarcodeFormat.PDF_417 },
      };
  
      barcodeScanView.OnScanResult += (result) =&gt;
      {
          barcodeScanView.IsScanning = false;
  
          Console.WriteLine(result);
  
          var data = result.Text.Split('\n');
  
          foreach (var line in data)
          {
  
              if (line.Length &gt; 3)
              {
                  var code = line.Substring(0, 3);
                  var value = line.Substring(3);
  
                  Xamarin.Forms.Device.BeginInvokeOnMainThread(() =&gt;
                  {
                      switch (code)
                      {
                          case "DCT":
                              userClass.Customer_Name = value.Trim();
                              Customer_Name.Text = value.Trim();
                              break;
                          case "DCS":
                              userClass.Customer_LName = value.Trim();
                              Customer_LName.Text = value.Trim();
                              break;
                          case "DAI":
                              userClass.City = value.Trim();
                              City.Text = value.Trim();
                              break;
                          case "DAG":
                              userClass.Address1 = value.Trim();
                              Address1.Text = value.Trim();
                              break;
                          case "DAK":
                              userClass.Zip = value.Trim();
                              Zip.Text = value.Trim();
                              break;
                      }
  
                  });
  
  
              }
          }
  
          ScanLicence.IsEnabled = true;
  
  
      };
  
      barcodeScanView.Options = options;
      barcodeScanView.IsScanning = true;
  
      ScannerWrapper.Children.Add(barcodeScanView);
  
  }
  </code></pre>
  
  <p>The button in question is <code>ScanLicence</code>.</p>
  
  <pre><code>&lt;Button x:Name="ScanLicence" Text="Scan Licence" Clicked="OnCameraScan" Style="{StaticResource ButtonStyle}" WidthRequest="50" /&gt;
  </code></pre>
  
  <p>This is for an iOS application.</p>