When you create an XML Web service in ASP.NET, you place the required @ WebService directive at the top of a text file with an .asmx file name extension. The presence of the .asmx file and the @ WebService directive correlate the URL address of the XML Web service with its implementation. Next, you implement the XML Web service class that defines the methods and data types visible by XML Web service clients. Finally, you add your XML Web service logic to those methods in order to process XML Web service requests and send back responses. The XML Web service class you define can be included directly in the .asmx file, or in a separate file. If you use a separate file, it must be compiled into an assembly. Optionally, you can apply a WebService attribute to the class implementing the XML Web service. The class that implements the XML Web service can derive from the WebService class.

To declare a Web service whose implementation resides in the same file

To declare a Web service whose implementation resides in an assembly

Classes that implement a Web service that was created using ASP.NET can optionally derive from the WebService class to gain access to the common ASP.NET objects, such as Application, Session, User, and Context.

<%@ WebService Language="C#" Class="Util" %>
using System;
using System.Web.Services;

public class Util: WebService 

<%@ WebService Language="VB" Class="Util" %>
Imports System
Imports System.Web.Services

Public Class Util
   Inherits WebService

Apply the optional WebService attribute to a class that implements a Web service to set the default XML namespace for the Web service, which originally is http://tempuri.org, along with a string to describe the Web service.

It is highly recommended that this default namespace, which is http://tempuri.org, be changed before the XML Web service is made publicly consumable. This is important because the XML Web service must be distinguished from other XML Web services that might inadvertently use the namespace as the default (<http://tempuri.org/>).

To set the XML namespace of which a Web service is a member

The following code example sets the XML namespace to http://www.contoso.com/.

<%@ WebService Language="C#" Class="Util" Debug=true%>
using System.Web.Services;
using System;

[WebService(Namespace="http://www.contoso.com/")]
public class Util: WebService 

<%@ WebService Language="VB" Class="Util"%>
Imports System.Web.Services
Imports System

<WebService(Namespace:="http://www.contoso.com/")> _
Public Class Util
    Inherits WebService

Methods of a class that implements a Web service do not automatically have the ability to be communicated with over the Web, but with Web services created using ASP.NET, it is very simple to add that capability. To add this capability, apply a WebMethod attribute to public methods. Methods of a Web service that can be communicated with over the Web are called Web service methods.

To declare a Web service method

The following code example has two public methods, one of which is a Web service method. The Multiply method is a Web service method, because it has a WebMethod attribute applied to it.

<%@ WebService Language="C#" Class="Util" %>
using System.Web.Services;
using System;

[WebService(Namespace="http://www.contoso.com/")]
public class Util: WebService 
{
    <b>[ WebMethod]</b>
<b>    public long Multiply(int a, int b) </b>
    {
        return a * b;
    }
}

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

Imports System.Web.Services
Imports System

<WebService(Namespace:="http://www.contoso.com/")> 
Public Class Util 
    Inherits WebService
    <<b> WebMethod()> _</b>
<b>    Public Function Multiply(a As Integer, b As Integer) As Long</b>
        Return a * b
    End Function
End Class

Reference

Concepts

Other Resources