The MessageName property can be used to alias method or property names. The most common use of the MessageName property will be to uniquely identify polymorphic methods. By default, MessageName is set to the name of the XML Web service method. Therefore, if an XML Web service contains two or more XML Web service methods with the same name, you can uniquely identify the individual XML Web service methods by setting the MessageName to a name unique within the XML Web service, without changing the name of the actual method name in code.

When data is passed to an XML Web service it is sent in a request and when it is returned it is sent in a response. Within the request and response, the name used for the XML Web service method is its MessageName property.

The message name associated with an XML Web service method must be unique within the XML Web service.

If a new XML Web serivce method with the same name but different parameters is added after clients are calling the original method, a different message name should be specified for the new method but the original message name should be left as is to ensure compatability with existing clients.

In the example below, MessageName is used to disambiguate the two Add methods.

<%@ WebService Language="VB" Class="Calculator" %>

Imports System
Imports System.Web.Services

Public Class Calculator
    Inherits WebService

    ' The MessageName property defaults to Add for this XML Web service method.
    <WebMethod()> _
    Overloads Public Function Add(i As Integer, j As Integer) As Integer

        Return i + j
    End Function

    <WebMethod(MessageName := "Add2")> _
    Overloads Public Function Add(i As Integer, j As Integer, k As Integer) As Integer

        Return i + j + k
    End Function    
End Class

<%@ WebService Language="C#" Class="Calculator" %>

 using System;
 using System.Web.Services;

 public class Calculator : WebService {
    // The MessageName property defaults to Add for this XML Web service method.
    [WebMethod]
    public int Add(int i, int j) {
       return i + j;
    }   
    [WebMethod(MessageName="Add2")]
    public int Add(int i, int j, int k) {
       return i + j + k;
    }   
 }

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC

.NET Framework

.NET Compact Framework

Reference