How to add custom SOAP header for C# Web service client invoke Axis 1.4 Web service

I'm trying to wirte a C# application as Webservice client invoke Java Web servie (use Axis 1.4) in 3 days but it's not work until now. Java WS require a custom SOAP header for authentication. So, I have to add a custom SOAP header in C# application. Code generated by VS 2010 do not include SOAP header, so I add a MySOAPHeader class into the project like that

namespace AddProvinceCityDemo
{
 [System.Xml.Serialization.XmlTypeAttribute(Namespace = "http://service.itthrm.vnitt.org")]
    [System.Xml.Serialization.XmlRootAttribute("securitytoken", Namespace = "http://service.itthrm.vnitt.org", IsNullable = false)]
    public class MySOAPHeader:SoapHeader
    {
        public String username;
        public String password;

    }
}

I also altered generated code in Reference.cs by adding MySOAPHeader varriable

public partial class ProvinceServiceClient : System.ServiceModel.ClientBase<AddProvinceCityDemo.ProvinceService.ProvinceService>, AddProvinceCityDemo.ProvinceService.ProvinceService {

        public MySOAPHeader customSOAPHeader;
        public ProvinceServiceClient() {
        }
         //.........................
}

Finally, I invoked WS by the following code

MySOAPHeader authentication = new MySOAPHeader();
 authentication.username = username;

  authentication.password = encryptedpass;
 //end set SOAP header information

 ProvinceServiceClient provinceservice = new ProvinceServiceClient();

 provinceservice.customSOAPHeader = authentication;
 Province[] arrprovince = null;

 arrprovince = provinceservice.findAll();

Below code throw an exception when it runs. Error message is "Failed to retreive the SOAP header"

Pls, help me to fix that bug.

I also tried to develop a Java application instead of C# application, and It's so simple like that

SOAPHeaderElement oHeaderElement;

oHeaderElement = new SOAPHeaderElement(namespace, "securityHeader");
oHeaderElement.setPrefix"sec");
oHeaderElement.setMustUnderstand(false);
oElement = oHeaderElement.addChildElement("username");
oElement.addTextNode(username);
oElement = oHeaderElement.addChildElement("password");
oElement.addTextNode(passwordEncrypt); 

How can I do the same in .net and C#?