Networking in Silverlight for Windows Phone

In Silverlight for Windows Phone, you can set the Accept, ContentLength, ContentType, or UserAgent headers of an HttpWebRequest using the dedicated property for that header.

Important Note:
You must set the Accept, header using the dedicated property. Attempting to set this header using the Headers collection will cause an ArgumentException to occur.

The following example shows how to set the User-agent header using the UserAgent property.

request.UserAgent = "appname";

In Windows Phone OS 7.1, if you compare the value of the ContentLength property to -1 to determine if the ContentLength header is set on an HttpWebResponse, you should compare the value as 64-bit and also 32-bit integers. To do this, you compare ContentLength with -1 as a 64-bit integer and then cast the value to a 32-bit integer and compare with -1. The following code example shows how to do this.

if (response.ContentLength == -1L || (Int32)response.ContentLength == -1)
{
   // The ContentLength header is not set. Handle this appropriately.
}

When you create a proxy class for a WCF service, you must do so at compile time. You cannot create a dynamic proxy. This is because the CreateChannel overloads are present, but not supported in Silverlight for Windows Phone. You can generate a compile-time proxy using slsvcutil.exe or the Add Service Reference feature in Visual Studio.

To generate a proxy using slsvcutil.exe:

1. Ensure that you use the slsvcutil.exe included with Visual Studio 2010 Express for Windows Phone.

2. Follow the steps described in Using SLsvcUtil.exe to Access a Service.

   Tip:

   When you use slsvcutil.exe to generate proxies and reference an assembly with the /reference option, the Web service you are generating a proxy for should be compiled using the .NET Framework or Silverlight compiler. If you compile the Web service with the Windows Phone SDK and try to create a proxy with slsvcutil.exe, an exception will occur. In this case, use Add Service Reference in Visual Studio to generate the proxy.

   Caution:
   If you encounter errors and you are not able to resolve them, make sure that you can access the Web service from a Silverlight browser-based application. If the issue is specific to Windows Phone, you may be able to find more specific help in the Windows Phone forums.

To generate a proxy using Add Service Reference:

1. Use Add Service Reference in a Windows Phone project that was created by using the Windows Phone SDK.

   Tip:
   The Add Service Reference function is provided by Microsoft.Silverlight.Phone.ServiceReference assembly that is available with the Windows Phone SDK. The Microsoft.Silverlight.ServiceReference assembly from the Silverlight SDK is not supported for use with Windows Phone applications.

   Tip:
   You should not run Visual Studio as an administrator. If you run Visual Studio as an administrator and you create a proxy using Add Service Reference, errors will occur.

2. Follow the steps described in How to: Access a Service from Silverlight.

   If you encounter errors and you are not able to resolve them, take the following steps:

   1. Stop and restart Visual Studio, and retry the scenario.

   2. Make sure that you can access the Web service from a Silverlight browser-based application. If the issue is specific to Windows Phone, you may be able to find more specific help in the Windows Phone forums.

   Tip:
   If you are generating a proxy to an authentication Web service and a WCF service, always generate the proxy to the WCF service first, and then the authentication service second. If you generate the proxy to the authentication service first, the proxy for the WCF service may not generate correctly.

There are a few implementation differences that you should be aware of when you call WCF services.

All BasicHttpSecurityMode values are supported. However, when you use the TransportWithMessageCredential value, you have to manually set the Basic authentication values for the Credentials property since UseDefaultCredentials specifies NTLM or digest authentication.

When you use OperationContext.Current.OutgoingMessageHeaders.Add to add headers to an outgoing Web service call, the headers will be overwritten when the call returns. This means that if you want to send the same headers for each Web service call, you need to add the headers each time you make a call.

Setting the MessageContractAttribute.IsWrapped property to false is not supported and will cause a service call to return null.

When you call a WCF service using basic authentication you need to set headers that contain the appropriate authentication information. The following code example shows an example of how to do this.

using (OperationContextScope contextScope = new OperationContextScope(svc.InnerChannel))
{
    byte[] bc = System.Text.Encoding.UTF8.GetBytes(@"username" + ":" + "password"); // the string passed after basic:
    HttpRequestMessageProperty httpProps = new HttpRequestMessageProperty();
    httpProps.Headers[HttpRequestHeader.Authorization] = "Basic " + Convert.ToBase64String(bc);
    OperationContext.Current.OutgoingMessageProperties[HttpRequestMessageProperty.Name] = httpProps;
    // call the service.
}

Using contextScope As New OperationContextScope(svc.InnerChannel)
    Dim bc As Byte() = 
        System.Text.Encoding.UTF8.GetBytes("username" & ":" & "password")
    'The string passed after basic:
    Dim httpProps As New HttpRequestMessageProperty()
    httpProps.Headers(HttpRequestHeader.Authorization) = "Basic " & 
        Convert.ToBase64String(bc)
    OperationContext.Current.OutgoingMessageProperties(
        HttpRequestMessageProperty.Name) = httpProps
    ' Call the service.
End Using

The following members in the System.ServiceModel namespace are not supported.

• ChannelFactory.InitializeEndpoint(ServiceEndpoint)

• ChannelFactory<TChannel>.CreateChannel()

• XmlSerializerFormatAttribute.SupportFaults

• XmlSerializerFormatAttribute.Style

There are some special considerations for the emulator or a device when you are testing applications that interact with WCF services.

• When you use HTTPS to access a WCF service for a Windows Phone application, you should make sure the current date and time of the emulator or device is in sync with the date and time on the computer hosting the Web service. Typically this is the case, but when the emulator starts there is a delay before the date and time is set on it. You should wait 1-2 minutes after you start the emulator to make sure that the date and time is set correctly before you try to call a Web service.

• If certificate installation is required by a Web service client, you will need to install the certificate on the device or emulator for the call to the service to return successfully. If a required certificate is not installed, the Web service may return a EndpointNotFoundException or ArgumentNullException.

• When you are testing applications that call Web services through a proxy with the emulator, you do not have access to fully-qualified domain names.