Presents your  
XML AND WEB SERVICES E-NEWSLETTER for November 24, 2003 
 
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DEFINE THE WEBMETHODATTRIBUTE CLASS   
  
When working with Web services in .NET, the most common practice for 
exposing a Web method is to denote that method with the default empty 
constructor <WebMethod()> attribute. However, there are several
different 
constructors and attributes you can assign to your Web service methods
that 
can radically affect performance and overall Web service layer design.  

  
We'll explore the six core attributes available when exposing a Web 
service method in Visual Studio .NET.   
  
THE ATTRIBUTES   
  
The WebMethodAttribute class defines six core public properties that 
you

can set in the <WebMethod()> constructor:   
  
* BufferResponse   
* CacheDuration   
* Description   
* EnableSession   
* MessageName   
* TransactionOption   
  
Let's review each property and see how they affect the behavior of your 
Web service methods.   
  
BufferResponse (Default = True)   
This attribute instructs the Web method to either wait until the entire 
response is serialized or to return the response as it's serialized.
When 
set to True, greater performance is achieved when returning fairly 
small

amounts of data back to the client.   
  
CacheDuration (Default = 0)   
This attribute sets the amount of time in seconds that the response is 
to be held in cache. If the Web method receives a request containing 
the

exact parameters as a previous request that still has its response
cached, 
the cached response is returned to the client immediately and the 
method

isn't executed. Be very careful when using this attribute, as it may 
cause adverse side effects by returning a cached response instead of a 
processed response.   
  
Description (Default = String.Empty)   
The Description property sets a string description for the Web method 
that service consumers may view when generating description documents
for 
the Web service, such as the WSDL file or the service help page.   
  
EnableSession (Default = False)   
This property indicates whether access to the session state object is 
enabled. When set to True, you may access the session object as you
would 
in any regular ASPX page. Enabling this property will likely cause 
performance to decrease.   
  
MessageName (Default = Name of the Web service method)   
If your Web service contains an overloaded method, you must use this 
property to set a unique name for each overloaded method; otherwise, 
the

WSDL will not be able to differentiate between the overloaded methods.  

  
TransactionOption (Default = Disabled)   
This attribute allows Web services to participate in transactions, but 
only as the root object in the creation of a new transaction process. 
To

gain access to the TransactionOption class, you must add the 
System.EnterpriseServices.dll reference to your project and import the 
System.EnterpriseServices class to your Web service.   
  
PROPERTIES IN ACTION   
  
LISTING 1.0 shows how to define each of these properties in the 
<WebMethod()> attribute. They can fall in any order or in any
combination you 
desire. For the sake of simplicity, we'll define a separate method for
each 
type of property.   
  
Listing 1.0   
  
<WebMethod(BufferResponse:=False)> _   
    Public Function GetLargeDataSet() As DataSet   
        ' code to retrieve and return a large amount of data   
    End Function   
  
    <WebMethod(CacheDuration:=60)> _   
    Public Function CachedFunction(ByVal Param1 As Integer, ByVal _   
                                   Param2 As Integer) As Integer   
        Return Param1 + Param2   
    End Function   
  
    <WebMethod(Description:="This method returns a string")> _   
    Public Function GetString() As String   
        Return "A String"   
    End Function   
  
    <WebMethod(EnableSession:=True)> _   
    Public Function TestSession() As String   
        If Session("UserState") Is Nothing Then   
            Session("UserState") = True   
            Return "This is the first time you have called this _   
                    function"   
        Else   
            Return "You have already called this method once during _   
                    your session"   
        End If   
    End Function   
  
    <WebMethod(MessageName:="MultiplyIntegers")> _   
    Public Function Multiply(ByVal Param1 As Integer, ByVal param2 As _ 

 
                             Integer) As Integer   
    End Function   
  
    <WebMethod(MessageName:="MultiplyLongs")> _   
    Public Function Multiply(ByVal Param1 As Long, ByVal Param2 As _   
                             Long) As Long   
    End Function   
  
    <WebMethod(TransactionOption:=TransactionOption.RequiresNew)> _   
    Public Sub TransactionFunction()   
        ' Code to perform multiple calls that form a single atomic 
transaction   
    End Sub   
  
UNDERSTAND THE DEFAULTS   
  
By understanding each property and its default value, you'll have a 
greater grasp of what behavior is being applied to your Web service
methods. 
Whether you like it or not, each of these six properties are being used 
on all of your Web methods with their default values when you denote 
the

method with the empty <WebMethod()> attribute.   
  
Kevin Koch is a senior software engineer with extensive experience in 
both Microsoft's .NET platform and J2EE technologies. He is a cofounder
and 
president of Task Solutions Inc.   
  
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