MVVM Combox Box not selecting the item if set selecteditem property in VM............Please help

<?page title="new page title" contentType="text/html;charset=UTF-8"?>
<zk>
	<window id="myWin" title="new page title" border="normal"
		apply="org.zkoss.bind.BindComposer"
		viewModel="@id('myvm') @init('mydomainUI.Example1VM')">
		<combobox model="@bind(myvm.users)"
			selectedItem="@bind(myvm.selectedUser)"
			onSelect="@command('ShowSelectedUser')">
			<template name="model" var="p1">
				<comboitem label="@bind(p1.userName)"
					value="@bind(p1.userCode)" />
			</template>
		</combobox>
		<button id="Submit" label="Show Selected User Code"
			onClick="@command('ShowSelectedUser')" />
	</window>
</zk>

package mydomainUI;

import java.util.ArrayList;
import java.util.List;
import org.zkoss.bind.annotation.Command;
import org.zkoss.bind.annotation.Init;
import org.zkoss.bind.annotation.NotifyChange;
import org.zkoss.zul.Messagebox;

import mydomain.users;

public class Example1VM {

	private List<users> allUsers= new ArrayList<users>();
	private users selectedUser = new users();
	
	public users getSelectedUser() {
		return selectedUser;
	}

	public void setSelectedUser(users selectedUser) {
		this.selectedUser = selectedUser;
	}

	@Command
	public void ShowSelectedUser()
	{
		Messagebox.show(this.selectedUser.getUserCode());
	}

	public List<users> getUsers() {
		
		users u1 = new users();
		u1.setUserName("John");
		u1.setUserCode("User101");
		u1.setUserPassword("xxxxx");
		u1.setFirstName("JohnFirstName");
		u1.setLastName("JohnLastName");
		u1.setHomePhone("1111111111");
		u1.setMobilePhone("222222");
		u1.setActive("Y");
		allUsers.add(u1);

		u1 = new users();
		u1.setUserName("Robert");
		u1.setUserCode("User102");
		u1.setUserPassword("xxxxx");
		u1.setActive("Y");
		u1.setFirstName("RobertFirstName");
		u1.setLastName("RobertLastName");
		u1.setHomePhone("53534343");
		u1.setMobilePhone("4534343");
		allUsers.add(u1);

		u1 = new users();
		u1.setUserName("Sean");
		u1.setUserCode("User103");
		u1.setUserPassword("xxxxx");
		u1.setActive("N");
		u1.setFirstName("SeanFirstName");
		u1.setLastName("SeanLastName");
		u1.setHomePhone("643434343");
		u1.setMobilePhone("64343445434");
		allUsers.add(u1);

		u1 = new users();
		u1.setUserName("Marry");
		u1.setUserCode("User104");
		u1.setUserPassword("xxxxx");
		u1.setActive("N");
		u1.setFirstName("MarryFirstName");
		u1.setLastName("MarryLastName");
		u1.setHomePhone("8644344");
		u1.setMobilePhone("44333");
		allUsers.add(u1);

		
		users u2 = new users();
		u2.setUserCode("User101");
		u2.setUserName("John");
		setSelectedUser(u2);

		return allUsers;
		
	}
}

package mydomain;

public class users {

	private String userCode;
	private String userName;
	private String userPassword;
	private String active;
	private String firstName;
	private String lastName;
	private String homePhone;
	private String mobilePhone;

	public String getFirstName() {
		return firstName;
	}

	public void setFirstName(String firstName) {
		this.firstName = firstName;
	}

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}

	public String getHomePhone() {
		return homePhone;
	}

	public void setHomePhone(String homePhone) {
		this.homePhone = homePhone;
	}

	public String getMobilePhone() {
		return mobilePhone;
	}

	public void setMobilePhone(String mobilePhone) {
		this.mobilePhone = mobilePhone;
	}

	public String getUserCode() {
		return userCode;
	}

	public void setUserCode(String userCode) {
		this.userCode = userCode;
	}

	public String getUserName() {
		return userName;
	}

	public void setUserName(String userName) {
		this.userName = userName;
	}

	public String getUserPassword() {
		return userPassword;
	}

	public void setUserPassword(String userPassword) {
		this.userPassword = userPassword;
	}

	public String getActive() {
		return active;
	}

	public void setActive(String active) {
		this.active = active;
	}

}