[C#]
[WebMethod]
public IAsyncResult BeginGetAuthorRoyalties(String Author,
AsyncCallback callback, object asyncState)
[Visual Basic]
＜WebMethod()＞ _
Public Function BeginGetAuthorRoyalties(ByVal Author As String, _
ByVal callback As AsyncCallback, ByVal asyncState As Object) _
As IAsyncResult

[C#]
[WebMethod]
public AuthorRoyalties EndGetAuthorRoyalties(IAsyncResult
asyncResult)

[Visual Basic]
＜WebMethod()＞ _
Public Function EndGetAuthorRoyalties(ByVal asyncResult As _
IAsyncResult) As AuthorRoyalties

[C#]
using System;
using System.Web.Services;
[WebService(Namespace="http://www.contoso.com/")]
public class MyService : WebService {
　public RemoteService remoteService;
　public MyService() {
　　// Create a new instance of proxy class for
　　// the XML Web service to be called.
　　remoteService = new RemoteService();
　}
　// Define the Begin method.
　 [WebMethod]
　public IAsyncResult BeginGetAuthorRoyalties(String Author,AsyncCallback callback, object asyncState) {
　　// Begin asynchronous communictation with a different XML Web
　　// service.
　　return remoteService.BeginReturnedStronglyTypedDS(Author,
　　callback,asyncState);
　}
　// Define the End method.
　[WebMethod]
　public AuthorRoyalties EndGetAuthorRoyalties(IAsyncResultasyncResult) {
　　// Return the asynchronous result from the other XML Web service.
　　return remoteService.EndReturnedStronglyTypedDS(asyncResult);
　}
}

[Visual Basic]
Imports System.Web.Services
＜WebService(Namespace:="http://www.contoso.com/")＞ _
Public Class MyService
Inherits WebService
Public remoteService As RemoteService

Public Sub New()
　MyBase.New()
　' Create a new instance of proxy class for
　' the XML Web service to be called.
　remoteService = New RemoteService()
End Sub

' Define the Begin method.
＜WebMethod()＞ _
Public Function BeginGetAuthorRoyalties(ByVal Author As String, _
ByVal callback As AsyncCallback, ByVal asyncState As Object) _
As IAsyncResult
　' Begin asynchronous communictation with a different XML Web
　' service.
　Return remoteService.BeginReturnedStronglyTypedDS(Author, _
　callback, asyncState)
End Function
' Define the End method.
＜WebMethod()＞ _
Public Function EndGetAuthorRoyalties(ByVal asyncResult As _
IAsyncResult) As AuthorRoyalties
　' Return the asynchronous result from the other XML Web service.
　Return remoteService.EndReturnedStronglyTypedDS(asyncResult)
End Function
End Class

[C#]
using System.Web.Services;
using System.Data;
using System;
// This imports the proxy class for the XML Web services
// that the sample communicates with.
using AsyncWS.localhost;

namespace AsyncWS
{
　[WebService(Namespace="http://www.contoso.com/")]
　public class MyService : System.Web.Services.WebService
　{
　　public RemoteService remoteService;
　　public MyService()
　　{
　　　remo　teService = new RemoteService();
　　}

　[WebMethod]
　public IAsyncResult BeginGetAuthorRoyalties(String Author,
　AsyncCallback callback, Object asyncState)
　{
　　// Saves the current state for the call that gets the author's
　　// royalties.
　　AsyncStateChain state = new AsyncStateChain();
　　state.originalState = asyncState;
　　state.Author = Author;
　　state.originalCallback = callback;

　　// Creates an intermediary callback.
　　AsyncCallback chainedCallback = new
　　AsyncCallback(AuthorRoyaltiesCallback);
　　return remoteService.BeginGetAuthors(chainedCallback,state);
　}
　// Intermediate method to handle chaining the
　// asynchronous calls.
　public void AuthorRoyaltiesCallback(IAsyncResult ar)
　{
　　AsyncStateChain state = (AsyncStateChain)ar.AsyncState;
　　RemoteService rs = new RemoteService();

　　// Gets the result from the call to GetAuthors.
　　Authors allAuthors = rs.EndGetAuthors(ar);

　　Boolean found = false;
　　// Verifies that the requested author is valid.
　　int i = 0;
　　DataRow row;
　　while (i ＜ allAuthors.authors.Rows.Count && !found)
　　{
　　　row = allAuthors.authors.Rows[i];
　　　if (row["au_lname"].ToString() == state.Author)
　　　{
　　　　found = true;
　　　}
　　　i++;
　　}
　　if (found)
　　{
　　　AsyncCallback cb = state.originalCallback;
　　　// Calls the second XML Web service, because the author is
　　　// valid.
　　　rs.BeginReturnedStronglyTypedDS(state.Author,cb,state);
　　}
　　else
　　{
　　　// Cannot throw the exception in this function or the XML Web
　　　// service will hang. So, set the state argument to the
　　　// exception and let the End method of the chained XML Web
　　　// service check for it.
　　　ArgumentException ex = new ArgumentException(
　　　　"Author does not exist.","Author");
　　　AsyncCallback cb = state.originalCallback;
　　　// Call the second XML Web service, setting the state to an
　　　// exception.
　　　rs.BeginReturnedStronglyTypedDS(state.Author,cb,ex);
　　}
　}

　[WebMethod]
　public AuthorRoyalties EndGetAuthorRoyalties(IAsyncResult asyncResult)
　{
　　// Check whehter the first XML Web service threw an exception.
　　if (asyncResult.AsyncState is ArgumentException)
　　　throw (ArgumentException) asyncResult.AsyncState;
　　else
　　　return remoteService.EndReturnedStronglyTypedDS(asyncResult);
　}
}
// Class to wrap the callback and state for the intermediate
// asynchronous operation.
public class AsyncStateChain
{
　public AsyncCallback originalCallback;
　public Object originalState;
　public String Author;
}
}

[Visual Basic]

Imports System.Web.Services
Imports System.Data
Imports System
' This imports the proxy class for the XML Web services
' that the sample communicates with.
Imports AsyncWS_VB.localhost

Namespace AsyncWs

＜WebService(Namespace:="http://www.contoso.com/")＞ _
Public Class MyService
Inherits WebService
Public remoteService As remoteService
Public Sub New()
MyBase.New()
remoteService = New localhost.RemoteService()
End Sub
' Defines the Begin method.
＜WebMethod()＞ _
Public Function BeginGetAuthorRoyalties(ByVal Author As String, _
ByVal callback As AsyncCallback, ByVal asyncState As Object) _
As IAsyncResult
' Saves the current state for the call that gets the author's
' royalties.
Dim state As AsyncStateChain = New AsyncStateChain()
state.originalState = asyncState
state.Author = Author
state.originalCallback = callback

' Creates an intermediary callback.
Dim chainedCallback As AsyncCallback = New AsyncCallback( _
AddressOf AuthorRoyaltiesCallback)
' Begin asynchronous communictation with a different XML Web
' service.
Return remoteService.BeginGetAuthors(chainedCallback, state)
End Function

' Intermediate method to handle chaining the asynchronous calls.
Public Sub AuthorRoyaltiesCallback(ByVal ar As IAsyncResult)
Dim state As AsyncStateChain = CType(ar.AsyncState, _
AsyncStateChain)
Dim rs As RemoteService = New RemoteService()

' Gets the result from the call to GetAuthors.
Dim allAuthors As Authors = rs.EndGetAuthors(ar)
Dim found As Boolean = False

' Verifies that the requested author is valid.
Dim i As Integer = 0
Dim row As DataRow
While (i ＜ allAuthors.authors.Rows.Count And (Not found))
　row = allAuthors.authors.Rows(i)
　If (row("au_lname").ToString() = state.Author) Then
　　found = True
　End If
　i = i + 1
End While

If (found) Then
　Dim cb As AsyncCallback = state.originalCallback
　' Calls the second XML Web service, because the author is
　' valid.
　rs.BeginReturnedStronglyTypedDS(state.Author, cb, state)
Else
　' Cannot throw the exception in this function or the XML Web
　' service will hang. So, set the state argument to the
　' exception and let the End method of the chained XML Web
　' service check for it.
　Dim ex As ArgumentException = New ArgumentException( "Author does not exist.", "Author")
　Dim cb As AsyncCallback = state.originalCallback
　' Call the second XML Web service, setting the state to an
　' exception.
　rs.BeginReturnedStronglyTypedDS(state.Author, cb, ex)
End If
End Sub

' Define the End method.
＜WebMethod()＞ _
Public Function EndGetAuthorRoyalties(ByVal asyncResult As _
IAsyncResult) As localhost.AuthorRoyalties
　' Return the asynchronous result from the other XML Web service.
　Return remoteService.EndReturnedStronglyTypedDS(asyncResult)
End Function

End Class

' Class to wrap the callback and state for the intermediate asynchronous
' operation.
Public Class AsyncStateChain
Public originalCallback As AsyncCallback
Public originalState As Object
Public Author As String
End Class
End Namespace