IWMSCacheProxyServerCallback.OnCompareContentInformation (Visual Basic .NET)

The OnCompareContentInformation method is called by the server to respond when a cache plug-in calls IWMSCacheProxyServer.CompareContentInformation.

IWMSCacheProxyServerCallback.OnCompareContentInformation(  lHr As Integer,
  CompareResponse As WMS_CACHE_VERSION_COMPARE_RESPONSE,
  pNewContentInfo As IWMSContext,
  varContext As Object
)

Arguments

	[in] Integer indicating whether the call to IWMSCacheProxyServer.CompareContentInformation succeeded.
	[in] Member of the WMS_CACHE_VERSION_COMPARE_RESPONSE enumeration type indicating the server response. This must be one of the following values.

Value	Description
WMS_CACHE_VERSION_FAIL_TO_CHECK_VERSION	There was a problem in checking the version. The cache plug-in should either delete the cached content, or try to compare versions again.
WMS_CACHE_VERSION_CACHE_STALE	The content is out of date. The cache plug-in must delete the cached content.
WMS_CACHE_VERSION_CACHE_UP_TO_DATE	The content is current. The content can be streamed.

	[in] IWMSContextIWMSContext Object (Visual Basic .NET) containing a Content Description Context. The context is associated with the URL passed when the plug-in calls CompareContentInformation.
	[in] Object containing a value defined by the plug-in when it called IWMSCacheProxyServer.CompareContentInformation. For example, your plug-in can use this parameter to persist state information. The server does not alter this value and passes it back when calling OnCompareContentInformation.

Return Value

This method does not return a value. To report an error, the plug-in can throw a COMException object to the server. If the plug-in uses the IWMSEventLogIWMSEventLog Object (C#) to log error information, it is recommended that it throw NS_E_PLUGIN_ERROR_REPORTED (0xC00D157D). Typically, the server attempts to make plug-in error information available to the server object model, the Windows Event Viewer, and the troubleshooting list in the details pane of the Windows Media Services MMC. However, if the plug-in uses the IWMSEventLog object to send custom error information to the Windows Event Viewer, throwing NS_E_PLUGIN_ERROR_REPORTED stops the server from also logging to the event viewer. For more information about plug-in error information, see Identifying Plug-in Errors.

Example

Imports Microsoft.WindowsMediaServices.Interop
Imports System.Runtime.InteropServices

Public Sub OnCompareContentInformation(ByVal lHr As Integer, _
                                       ByVal CompareResponse As WMS_CACHE_VERSION_COMPARE_RESPONSE, _
                                       ByVal NewContentInfo As IWMSContext, _
                                       ByVal varContext As Object) _
  Implements IWMSCacheProxyServerCallback.OnCompareContentInformation

    Dim Response As WMS_CACHE_QUERY_RESPONSE
    Dim ci As ContentInfo
    Dim Context As IWMSContext
    Dim nIndex As Integer
    Dim strCacheUrl As String

    Try

        ' Set the response equal to a cache miss.
        Response = WMS_CACHE_QUERY_RESPONSE.WMS_CACHE_QUERY_MISS

        ' Retrieve the user defined ContentInfo object
        ' from the varContext parameter.
        ci = varContext

        ' The call to IWMSCacheProxyServer.CompareContentInfo succeeded.
        If lHr = 0 Then

            Select Case CompareResponse

                Case WMS_CACHE_VERSION_COMPARE_RESPONSE.WMS_CACHE_VERSION_CACHE_STALE
                    ' The content has expired. Remove it from the DataSet object.
                    RemoveEntryFromDataBase(ci, True)

                Case WMS_CACHE_VERSION_COMPARE_RESPONSE.WMS_CACHE_VERSION_CACHE_UP_TO_DATE
                    ' The content is current.
                    If (ci.ContentType And 1) <> 0 Then
                        ' Broadcast content.
                        Response = WMS_CACHE_QUERY_RESPONSE.WMS_CACHE_QUERY_HIT_PLAY_BROADCAST
                    Else
                        ' On-demand content.
                        Response = WMS_CACHE_QUERY_RESPONSE.WMS_CACHE_QUERY_HIT_PLAY_ON_DEMAND
                    End If

                    ' Update the DataTable object with new information.
                    ' The RemoveEntryFromDataBase(), GetContentInfoFromContext(),
                    ' and UpdateTable() functions are user-defined.
                    RemoveEntryFromDataBase(ci, False)
                    GetContentInfoFromContext(NewContentInfo, ci)
                    UpdateTable(ci)
                    GetContentInfoContext(ci, Context)

                Case WMS_CACHE_VERSION_COMPARE_RESPONSE.WMS_CACHE_VERSION_FAIL_TO_CHECK_VERSION
                    ' The server did not check version information.
            End Select

            ' Specify the cache URL. A basic starting point searches for
            ' the :// character sequence in the URL. If this sequence is
            ' not found, prefix the URL with file://.
            nIndex = ci.CacheUrl.IndexOf("://")
            If nIndex = -1 Then
                strCacheUrl = String.Format("file://", ci.CacheUrl)
            End If

            ' Send the response to the server.
            ci.CacheProxyCallback.OnQueryCache(0, _
                                               Response, _
                                               strCacheUrl, _
                                               Context, _
                                               Nothing, _
                                               ci.varContext)
        End If

    Catch
        Throw New COMException()
    End Try

End Sub

Requirements

Reference: Add a reference to Microsoft.WindowsMediaServices.

Namespace: Microsoft.WindowsMediaServices.Interop.

Assembly: Microsoft.WindowsMediaServices.dll.

Library: WMSServerTypeLib.dll.

Platform: Windows Server 2003, Enterprise Edition; Windows Server 2003, Datacenter Edition; Windows Server 2008.

See Also

Concepts

IWMSCacheProxyServerCallback Object (Visual Basic .NET)