<OperationContractAttribute(AsyncPattern=True, 
   Action="http://opcfoundation.org/UA/2008/02/Services.wsdl/Cancel", 
   ReplyAction="http://opcfoundation.org/UA/2008/02/Services.wsdl/CancelResponse")>
<FaultContractAttribute(Action="http://opcfoundation.org/UA/2008/02/Services.wsdl/CancelFault", 
   Name="ServiceFault", 
   Namespace="http://opcfoundation.org/UA/2008/02/Types.xsd", 
   DetailType=Opc.Ua.ServiceFault, 
   ProtectionLevel=ProtectionLevel.None, 
   HasProtectionLevel=False)>
Function BeginCancel( _
   ByVal request As CancelMessage, _
   ByVal callback As AsyncCallback, _
   ByVal asyncState As Object _
) As IAsyncResult

[OperationContractAttribute(AsyncPattern=true, 
   Action="http://opcfoundation.org/UA/2008/02/Services.wsdl/Cancel", 
   ReplyAction="http://opcfoundation.org/UA/2008/02/Services.wsdl/CancelResponse")]
[FaultContractAttribute(Action="http://opcfoundation.org/UA/2008/02/Services.wsdl/CancelFault", 
   Name="ServiceFault", 
   Namespace="http://opcfoundation.org/UA/2008/02/Types.xsd", 
   DetailType=Opc.Ua.ServiceFault, 
   ProtectionLevel=ProtectionLevel.None, 
   HasProtectionLevel=false)]
IAsyncResult BeginCancel( 
   CancelMessage request,
   AsyncCallback callback,
   object asyncState
)