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LicenseAcquirer Class

Silverlight

This class handles acquiring PlayReady licenses for protected content.

System.Object
  System.Windows.Media.LicenseAcquirer

Namespace:  System.Windows.Media
Assembly:  System.Windows (in System.Windows.dll)

'Declaration
Public Class LicenseAcquirer

The LicenseAcquirer type exposes the following members.

  NameDescription
Public methodSupported by Silverlight for Windows PhoneLicenseAcquirerInitializes a new instance of the LicenseAcquirer class.
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  NameDescription
Public propertyChallengeCustomDataGets or sets a string that contains service-specific data to be conveyed to the license server without implementing manual license acquisition.
Public propertyDomainAcquirerGets or sets a DomainAcquirer to handle Join Domain requests that are triggered from License Server exceptions (DomainRequired or RenewDomain).
Public propertyInjectClientInformationGets or sets a value that indicates whether identifiable client information is injected into the license acquisition.
Public propertySupported by Silverlight for Windows PhoneLicenseServerUriOverrideGets or sets a Uniform Resource Identifier (URI) value that overrides whatever the license server URI is in the content header.
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  NameDescription
Public methodAcquireLicenseAsync(Byte())Starts the license acquisition process.
Public methodAcquireLicenseAsync(Guid)Starts the license acquisition process.
Public methodAcquireLicenseAsync(Stream)Starts the license acquisition process by specifying a media stream.
Public methodAcquireLicenseAsync(Guid, ContentKeyType, Guid)Starts the license acquisition process.
Public methodCancelAsyncCancels a license acquisition.
Public methodSupported by Silverlight for Windows PhoneEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows PhoneFinalizeAllows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by Silverlight for Windows PhoneGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodSupported by Silverlight for Windows PhoneGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows PhoneMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Protected methodSupported by Silverlight for Windows PhoneOnAcquireLicenseThe default implementation of this method calls into the MediaElement to acquire a license. You should override this method if you want to handle the license acquisition yourself.
Protected methodSupported by Silverlight for Windows PhoneOnCancelOverridden in a derived class to implement cancellation during manual license acquisition.
Protected methodSupported by Silverlight for Windows PhoneSetLicenseResponseSets the license response by passing the SOAP body from the HTTP response to the license challenge.
Public methodSupported by Silverlight for Windows PhoneToStringReturns a string that represents the current object. (Inherited from Object.)
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  NameDescription
Public eventAcquireLicenseCompletedOccurs when the license acquisition completes.
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This class knows where to find the PlayReady License Server and how to request a license from that server. This class can be subclassed and overridden to provide custom license-acquiring behavior, such as adding business data or authentication tokens to the request.

NoteNote:

If you start multiple asynchronous operations on the same LicenseAcquirer or DomainAcquirer, an InvalidOperationException is thrown.

You can use a LicenseAcquirer instance in one of the following two states:

  1. Attached to a MediaElement.

  2. Through AcquireLicenseAsync methods calls.

If you use a LicenseAcquirer instance in state 1, then for the rest of its lifetime, you can only use it through that MediaElement. You cannot reassign the LicenseAcquirer instance to another MediaElement and you cannot use it with the AcquireLicenseAsync methods.

If you use a LicenseAcquirer instance through AcquireLicenseAsync methods calls, then it cannot be assigned to a MediaElement even after the AcquireLicenseAsync operation has fully completed.

When you create a LicenseAcquirer instance, it is in neither state 1 nor state 2. State 1 is only entered when the LicenseAcquirer instance is actually assigned to the MediaElement. State 2 is entered when AcquireLicenseAsync is first called (regardless of success or failure of the operation).

The LicenseAcquirer class is used by the MediaElement to handle acquiring licenses for DRM encrypted content from a PlayReady License Server. You can create a derived class from the LicenseAcquirer class and add custom logic like adding your own custom authentication scheme to the license request.

The following example shows how to override the LicenseAcquirer class (named "ManualLicenseAcquirer") and have a MediaElement use it to acquire the license.

<StackPanel x:Name="LayoutRoot" Background="Gray" Orientation="Vertical">
   <MediaElement x:Name="myME" Height="100"/>
</StackPanel>
Public Class Page
    Inherits UserControl
    
    Public Sub New()
        MyBase.New
        InitializeComponent
        AddHandler Loaded, AddressOf Me.Page_Loaded
    End Sub
    
    Private Sub Page_Loaded(ByVal sender As Object, ByVal e As RoutedEventArgs)
        ' Test a full fledged manual acquirer
        ' Set the LicenseAcquirer of the MediaElement to the custom License Acquirer
        ' defined in this sample.
        myME.LicenseAcquirer = New ManualLicenseAcquirer(myME.Name)
        ' Set the License URI to proper License Server address.
        myME.LicenseAcquirer.LicenseServerUriOverride = New Uri("http://contoso.com/myLicenseServer.asmx", UriKind.Absolute)
        AddHandler myME.MediaFailed, AddressOf Me.myME_MediaFailed
        ' Set the source of the MediaElement to the URL of the media encrypted with WMDRM.
        myME.Source = New Uri("http:, contoso.com/wmdrm_url.wmv", UriKind.Absolute);)
    End Sub
    
    Private Sub myME_MediaFailed(ByVal sender As Object, ByVal e As ExceptionRoutedEventArgs)
        Dim errorMessage As String = ""
        If e.ErrorException.ToString.Contains(" 6001 ") Then
            errorMessage = "The individualization component software failed to" & _
                           " download to the user's computer. This error would" & _
                           " come up when the MediaElement is in the Individualizing" & _
                           " MediaElementState. One possible reason for this error is" & _
                           " that the Silverlight client cannot connect the Microsoft" & _
                           " Individualization Server."
        ElseIf e.ErrorException.ToString.Contains(" 6004 ") Then
            errorMessage = "The installation of Silverlight on the client is" & _
                           " out of date and needs to be updated."
        Else
            errorMessage = "MediaFailed: " & _
                        +  e.ErrorException.Message + "."
        End If
        System.Windows.Browser.HtmlPage.Window.Alert(errorMessage)
    End Sub
    
    ' makes license request explicitly
    Public Class ManualLicenseAcquirer
        Inherits LicenseAcquirer
        
        Private challengeString As String
        
        Private _mediaElementName As String
        
        Public Sub New(ByVal mediaElementName As String)
            MyBase.New
            _mediaElementName = mediaElementName
        End Sub
        
        ' The default implementation of OnAcquireLicense calls into the MediaElement to acquire a
        '  license. It is called when the Media pipeline is building a topology and will be raised
        ' before MediaOpened is raised.
        Protected Overrides Sub OnAcquireLicense(ByVal licenseChallenge As System.IO.Stream, ByVal licenseServerUri As Uri)
            Dim sr As StreamReader = New StreamReader(licenseChallenge)
            challengeString = sr.ReadToEnd
            ' Need to resolve the URI for the License Server -- make sure it is correct
            ' and store that correct URI as resolvedLicenseServerUri.
            Dim resolvedLicenseServerUri As Uri
            If (LicenseServerUriOverride Is Nothing) Then
                resolvedLicenseServerUri = licenseServerUri
            Else
                resolvedLicenseServerUri = LicenseServerUriOverride
            End If
            ' Make a HttpWebRequest to the License Server.
            Dim request As HttpWebRequest = CType(WebRequest.Create(resolvedLicenseServerUri),HttpWebRequest)
            request.Method = "POST"
            ' Set ContentType through property    
            request.ContentType = "application/xml"
            '  ADD REQUIRED HEADERS.
            ' The headers below are necessary so that error handling and redirects are handled 
            ' properly via the Silverlight client.
            request.Headers("msprdrm_server_redirect_compat") = "false"
            request.Headers("msprdrm_server_exception_compat") = "false"
            '  Initiate getting request stream  
            Dim asyncResult As IAsyncResult = request.BeginGetRequestStream(New AsyncCallback(RequestStreamCallback), request)
        End Sub
        
        ' This method is called when the asynchronous operation completes.
        Private Sub RequestStreamCallback(ByVal ar As IAsyncResult)
            Dim request As HttpWebRequest = CType(ar.AsyncState,HttpWebRequest)
            ' populate request stream  
            request.ContentType = "text/xml"
            Dim requestStream As Stream = request.EndGetRequestStream(ar)
            Dim streamWriter As StreamWriter = New StreamWriter(requestStream, System.Text.Encoding.UTF8)
            streamWriter.Write(challengeString)
            streamWriter.Close
            ' Make async call for response  
            request.BeginGetResponse(New AsyncCallback(ResponseCallback), request)
        End Sub
        
        Private Sub ResponseCallback(ByVal ar As IAsyncResult)
            Dim request As HttpWebRequest = CType(ar.AsyncState,HttpWebRequest)
            Dim response As WebResponse = request.EndGetResponse(ar)
            SetLicenseResponse(response.GetResponseStream)
        End Sub
    End Class
End Class

In offline scenarios, users download a content file before they play it. Because downloading a media file can take time and bandwidth, consider validating the user license before allowing the download, instead of validating when the user attempts playback. The following example shows how to do this.

The following application uses a key identifier and an authentication token to send a license acquisition request to the license server. The license server responds with a license and the URL from which to download the content.

// Called when the user is online and wants to download some protected content.
public void GetLicensePreDelivery(string customData,
                                     Guid keyId)
{
    Uri licenseServerUrl = new Uri("http://contoso.com/myLicenseServer.asmx");
    LicenseAcquirer acquirer = new LicenseAcquirer();
    acquirer.ChallengeCustomData = customData;

    // Set the License URI to proper License Server address.
    acquirer.LicenseServerUriOverride = licenseServerUrl;
    acquirer.AcquireLicenseCompleted += new EventHandler<AcquireLicenseCompletedEventArgs>(acquirer_Completed);
    acquirer.AcquireLicenseAsync(keyId, ContentKeyType.Aes128Bit, Guid.Empty);
}

The AcquireLicenseAsync call completes after starting the license acquisition but without waiting for the long content download operation to finish. When the license acquisition actually completes, the delegate that is configured on the AcquireLicenseCompleted event is called. In this example, that is the acquirer_Completed method, and it might look something like in the following example.

public void acquirer_Completed(object sender, AcquireLicenseCompletedEventArgs e)
{
    if (e.Error != null)
    {
        // take appropriate action.  Might be retrying for instance.
    }
    else if (e.Cancelled)
    {
        // take appropriate action.  Might be nothing.
    }
    else
    {
        //
        //  We acquired the license successfully, go ahead and download
        //  the content.  Note the service decided to stash the content 
        //  url in the LicenseAcquirer response custom data.
        //
        string contentAcquisitionUrl = e.ResponseCustomData;
        DownloadContent(contentAcquisitionUrl);
    

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, 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.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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