Dim instance As Service
Dim request As WriteRequest
Dim callback As AsyncCallback
Dim asyncState As Object
Dim value As IAsyncResult
 
value = instance.BeginWrite(request, callback, asyncState)

[OperationContractAttribute(AsyncPattern=true, 
   Action="http://opcfoundation.org/webservices/XMLDA/1.0/Write", 
   ReplyAction="*")]
IAsyncResult BeginWrite( 
   WriteRequest request,
   AsyncCallback callback,
   object asyncState
)