Problem with SOAP headers

[Mikaelo]

When i use web method i must send header to it
in wsdl i have

<import namespace="http://schemas.xmlsoap.org/soap/encoding/" />
- <complexType name="userContext">
- <sequence>
<element name="name" nillable="true" type="soapenc:string" />
<element name="password" nillable="true" type="soapenc:string" />
</sequence>
</complexType>

Visual Studion generate proxy (part)
[System.Xml.Serialization.SoapTypeAttribute("userCo ntext",
"http:/www.umike.ru/site/web")]
public class userContext : SoapHeader {

/// <remarks/>
public string name;

/// <remarks/>
public string password;
}

when i send this class as header
<tns:userContext id="id1" soap:mustUnderstand="1"><name
xsi:type="xsd:string">DEMOUSER</name><password
xsi:type="xsd:string">DEMOUSER</password></tns:userContext>

and when in body
<tns:userContext id="id1" soap:mustUnderstand="1" xsi:type="tns:userContext"

<name xsi:type="xsd:string">DEMOUSER</name><password

xsi:type="xsd:string">DEMOUSER</password></tns:userContext>

why element xsi:type="tns:userContext" is absent in header ?

Thank you