Public Event DownloadStringCompleted As EventHandler(Of ArcGISWebClient.DownloadStringCompletedEventArgs)

public event EventHandler<ArcGISWebClient.DownloadStringCompletedEventArgs> DownloadStringCompleted

<Grid x:Name="LayoutRoot" Background="White">
  
  <!-- Url for the ArcGISWebClient operation. -->
  <TextBox Height="44" HorizontalAlignment="Left" Margin="4,181,0,0" Name="TextBox_Url" VerticalAlignment="Top" Width="575" 
  Text="http://services.arcgisonline.com/ArcGIS/rest/services/Demographics/USA_Median_Age/MapServer/4/query?where=1%3D1&amp;returnCountOnly=true&amp;f=json"
  TextWrapping="Wrap"/>
  
  <!-- Button to perform the work. -->
  <Button Content="DownloadStringAsync" Height="24" Width="201" HorizontalAlignment="Left" Margin="4,232,0,0" 
          Name="Button_DownloadStringAsync" VerticalAlignment="Top" Click="Button_DownloadStringAsync_Click" />
  
  <!-- CheckBox option to display the ArcGISWebClient Response JSON in a MessageBox or TextBox.-->
  <CheckBox Content="Display Results in a MessageBox" Height="16" HorizontalAlignment="Left" Margin="211,235,0,0" 
            Name="CheckBox1" VerticalAlignment="Top" />
  
  <!-- Display the Response for the ArcGISWebClient operation. -->
  <TextBox Height="95" HorizontalAlignment="Left" Margin="4,262,0,0" Name="TextBox_Response" 
           VerticalAlignment="Top" Width="575" VerticalScrollBarVisibility="Auto" 
           HorizontalScrollBarVisibility="Auto" />
  
  <!-- Provide the instructions on how to use the sample code. -->
  <TextBlock Height="94" HorizontalAlignment="Left" Name="TextBlock1" VerticalAlignment="Top" Width="625" 
  TextWrapping="Wrap" Text="Click the 'DownloadStringAsync' Button to start an ArcGISWebClient operation. Check 
  'on' the CheckBox if you want to see the JSON results in a MessageBox, otherwise the result will
  display in the TextBox. The JSON result returned is a count of the number of features in a FeatureLayer." />
  
</Grid>

private void Button_DownloadStringAsync_Click(object sender, System.Windows.RoutedEventArgs e)
{
  // Clear out any existing information in the TextBox.
  TextBox_Response.Text = "";
  
  // Create a new ArcGISWebClient object.
  ESRI.ArcGIS.Client.ArcGISWebClient myArcGISWebClient = new ESRI.ArcGIS.Client.ArcGISWebClient();
  
  // Wire up an Event Handler for the ArcGISWebClient.DownloadStringCompleted Event.
  myArcGISWebClient.DownloadStringCompleted += arcgisWebClient_DownloadStringCompleted;
  
  // Get the Url for the ArcGISWebClient request.
  string myUrl = TextBox_Url.Text;
  
  // Get the userState (aka. user token) to determine how to display the results of the ArcGISWebClient operation.
  bool myUserToken = (bool)CheckBox1.IsChecked;
  
  // Invoke the ArcGISWebClient.DownloadStringAsync Method passing in the Url, nothing for the parameter collection, and a user token.
  // This ArcGISWebClient operation is very small, use the HttpMethods.Get enumeration. You could leave
  // this parameter unspecified, which will by default use the HttpMethods.Auto enumeration. HttpMethods.Auto lets
  // the application choose the best communication method to use based upon the request being made and the 
  // capabilities of the client host container.
  myArcGISWebClient.DownloadStringAsync(new Uri(myUrl), null, ESRI.ArcGIS.Client.ArcGISWebClient.HttpMethods.Get, myUserToken);
}
            
private void arcgisWebClient_DownloadStringCompleted(object sender, ESRI.ArcGIS.Client.ArcGISWebClient.DownloadStringCompletedEventArgs e)
{
  // Get the userState (aka. user token) from the ArcGISWebClient operation.
  bool myUserToken = (bool)e.UserState;
  
  // Get the JSON string result from the ArcGISWebClient operation.
  string theResult = e.Result;
  
  if (myUserToken == true)
  {
    // Display the JSON string response in a MessageBox.
    MessageBox.Show(theResult);
  }
  else
  {
    // Display the JSON string response in the TextBox.
  TextBox_Response.Text = theResult;
  }
}

Private Sub Button_DownloadStringAsync_Click(sender As System.Object, e As System.Windows.RoutedEventArgs)
  
  ' Clear out any existing information in the TextBox.
  TextBox_Response.Text = ""
  
  ' Create a new ArcGISWebClient object.
  Dim myArcGISWebClient As ESRI.ArcGIS.Client.ArcGISWebClient = New ESRI.ArcGIS.Client.ArcGISWebClient
  
  ' Wire up an Event Handler for the ArcGISWebClient.DownloadStringCompleted Event.
  AddHandler myArcGISWebClient.DownloadStringCompleted, AddressOf arcgisWebClient_DownloadStringCompleted
  
  ' Get the Url for the ArcGISWebClient request.
  Dim myUrl As String = TextBox_Url.Text
  
  ' Get the userState (aka. user token) to determine how to display the results of the ArcGISWebClient operation.
  Dim myUserToken As Boolean = CheckBox1.IsChecked
  
  ' Invoke the ArcGISWebClient.DownloadStringAsync Method passing in the Url, nothing for the parameter collection, and a user token.
  ' This ArcGISWebClient operation is very small, use the HttpMethods.Get enumeration. You could leave
  ' this parameter unspecified, which will by default use the HttpMethods.Auto enumeration. HttpMethods.Auto lets
  ' the application choose the best communication method to use based upon the request being made and the 
  ' capabilities of the client host container.
  myArcGISWebClient.DownloadStringAsync(New Uri(myUrl), Nothing, ESRI.ArcGIS.Client.ArcGISWebClient.HttpMethods.Get, myUserToken)
  
End Sub
            
Private Sub arcgisWebClient_DownloadStringCompleted(sender As Object, e As ESRI.ArcGIS.Client.ArcGISWebClient.DownloadStringCompletedEventArgs)
  
  ' Get the userState (aka. user token) from the ArcGISWebClient operation.
  Dim myUserToken As Boolean = e.UserState
  
  ' Get the JSON string result from the ArcGISWebClient operation.
  Dim theResult As String = e.Result
  
  If myUserToken = True Then
    
    ' Display the JSON string response in a MessageBox.
    MessageBox.Show(theResult)
    
  Else
     
    ' Display the JSON string response in the TextBox.
    TextBox_Response.Text = theResult
    
  End If
  
End Sub