First problem is solved by Making password as XMLText and PasswordType as XMLAttribute inside Password Class, then it geenrated XML correctly. Still not getting Namespace of BSVC Inside Body Attributes:
public class UsernameToken
{
[XmlElement("Username")]
public string Username { get; set; }
[XmlElement("Password")]
public PasswordData Password { get; set; }
}
public class PasswordData
{
[XmlText]
public string Password { get; set; }
[XmlAttribute("Type")]
public string PasswordType { get; set; }
}