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NetworkInterface.GetIsNetworkAvailable Method

Indicates whether any network connection is available.

Namespace:  System.Net.NetworkInformation
Assembly:  System.Net (in System.Net.dll)

[SecuritySafeCriticalAttribute]
public static bool GetIsNetworkAvailable()

Return Value

Type: System.Boolean
true if a network connection is available; otherwise, false.

A network connection is considered to be available if any network interface is marked "up" and is not a loopback or tunnel interface.

There are many cases in which a device or computer is not connected to a useful network but is still considered available and GetIsNetworkAvailable will return true. For example, if the device running the application is connected to a wireless network that requires a proxy, but the proxy is not set, GetIsNetworkAvailable will return true. Another example of when GetIsNetworkAvailable will return true is if the application is running on a computer that is connected to a hub or router where the hub or router has lost the upstream connection.

The following example uses the GetIsNetworkAvailable method to determine if a network connection is available.


public class Example
{
  static bool online = false; 

  public static void Demo(System.Windows.Controls.TextBlock outputBlock)
  {

      // Initialize the online variable and set a NetworkChange handler
      SetupNetworkChange();

      outputBlock.Text += "Network is: ";
      if (online)
          outputBlock.Text += "online";
      else     
          outputBlock.Text += "offline";

      // Now start the main work of the application        
  }

  // method that gets called when the network changes
  static void OnNetworkChange(object sender, EventArgs e)
  {
     if (NetworkInterface.GetIsNetworkAvailable())
     {
         if (!online)
          {
             online = true;
             // do what is needed to GoOnline();
          }
     }
     else {
         if (online)
         {
             online = false;
             // do what is needed to GoOffline();
         }
     }
  }

  private static void SetupNetworkChange()
  {
     // Get current network availalability and store the 
     // initial value of the online variable
     if (NetworkInterface.GetIsNetworkAvailable())
     {
         online = true;
         // do what is needed to GoOnline();
     }
     else
     {
         online = false;
         // do what is needed to GoOffline();
     }

      // Now add a network change event handler to indicate
      // network availability 
      NetworkChange.NetworkAddressChanged +=
          new NetworkAddressChangedEventHandler(OnNetworkChange);
  }
}


Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Windows Phone OS 7.0

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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