Hi,
My name is Giuliano Greco and I am a Italian engineer.
I bought the book Professional ASP.NET 4 in C # and VB and I was growing
the example of chapter 31 "Working with Services" precisely as:
Using SOAP Headers created a class which is a web service and then HelloHeader
HelloSoapHeader.asmx. Then, we create a page .aspx where it is consumed
service with this code:
<%@ Page Language="C#" %>

<script runat="server">
protected void Page_Load(object sender, System.EventArgs e) {
localhost.HelloSoapHeader ws = new localhost.HelloSoapHeader();
localhost.HelloHeader wsHeader = new localhost.HelloHeader();
wsHeader.Username = "Bill Evjen";
wsHeader.Password = "Bubbles";
ws.HelloHeaderValue = wsHeader;
Label1.Text = ws.HelloWorld();
}
</script>

I can not understand where the property is located in the class since HelloHeaderValue
is not defined?

In all the examples of your books do not have this property.