动态调用webservice时如何验证身份？

[zqsntws]

原文：http://www.cnblogs.com/RainWaterLily/archive/2008/01/27/1055099.html
的确很牛，可以实现动态调用webservice。但有个问题：如何设置身份验证？哪位达人可以告知，谢谢！
VB中实现的代码如下：
定义个类：clsSoapHeaderHandler

Implements IHeaderHandler
Option Explicit

'used for verification in webservice
Public AuthUser As String 'user name
Public AuthPassword As String 'user password
Private Function IHeaderHandler_readHeader(ByVal par_Reader As MSSOAPLib30.ISoapReader, ByVal par_HeaderNode As MSXML2.IXMLDOMNode, ByVal par_Object As Object) As Boolean
IHeaderHandler_readHeader = False
End Function
Private Function IHeaderHandler_WillWriteHeaders() As Boolean
IHeaderHandler_WillWriteHeaders = True
End Function
Private Sub IHeaderHandler_writeHeaders( _
ByVal pSerializer As SoapSerializer30, _
ByVal pObject As Object)

'generate SOAP XML request message
pSerializer.StartHeaderElement "Authentication", "http://www.ibm.com"

pSerializer.StartElement "Username" 'Matching with SERVICE code
pSerializer.WriteString AuthUser
pSerializer.EndElement

pSerializer.StartElement "Password"
pSerializer.WriteString AuthPassword
pSerializer.EndElement

pSerializer.EndHeaderElement
End Sub

调用的地方：

dim objHeaderHandler as New clsSoapHeaderHandler
dim mysoapClient as SoapClient30

objHeaderHandler.AuthUser = "username"
objHeaderHandler.AuthPassword = "pws"
Set mysoapClient.HeaderHandler = objHeaderHandler
这样就可以把验证信息传给服务器，动态调用webservice时如何把这段转成C#代码？

[zqsntws]

请大家帮帮忙。

[zqsntws]

第一个回答的就给80分。