<soap:Header>
  <UserSoapHeader xmlns="http://tempuri.org/">
   <UserName>string</UserName>
   <Pwd>string</Pwd>
  </UserSoapHeader>
</soap:Header>

public class UserSoapHeader : SoapHeader
{
  private string _userName;
  private string _pwd;
 
  //public的属性将自动生成xml结点
  public string UserName
  {
    get { return _userName; }
    set { _userName = value; }
  }
 
  public string Pwd
  {
    get { return _pwd; }
    set { _pwd = value; }
  }
}

/// <summary>
/// WebService 的摘要说明
/// </summary>
[WebService(Namespace = "http://tempuri.org/")]
[WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)]
public class WebService : System.Web.Services.WebService
{
//此属性将作为验证属性
//方法的SoapHeaderAttribute中的名称与此变量一致
  public UserSoapHeader userHeader;
 
  public WebService()
  {
    //如果使用设计的组件，请取消注释以下行
    //InitializeComponent();
  }
 
  [WebMethod]
  [SoapHeader("userHeader")]//这里很重要，名称要和定义的验证属性名称一致!
  public string HelloWorld()
  {
    //进入此方法后，userHeader将自动有值
    if (userHeader != null)
    {
      return "this is retVal : " + userHeader.UserName;
    }
    return " check not successed ";
  }
}

WebService s = new WebService();
    UserSoapHeader a = new UserSoapHeader();
    a.UserName = "admin";
    a.Pwd = "zz";
    s.UserSoapHeaderValue = a; //此属性是自动生成的
    Response.Write( s.HelloWorld() ); // this is retVal : admin