get error namespace not defined

I get error sample( which is my namespace) is not defined 
 .asmx file


<%@ WebService Language="VB" CodeBehind="~/App_Code/service.vb" Class="sample.com" %>

Imports System.Web
Imports System.Web.Services
Imports System.Xml
Imports System.Web.Services.Protocols
Imports System.Web.Script.Services
Imports System.Web.Services.WebService

Namespace sample
    <WebService(Namespace:="http://tempuri.org/")> _
    <WebServiceBinding(ConformsTo:=WsiProfiles.BasicProfile1_1)> _
    <Global.Microsoft.VisualBasic.CompilerServices.DesignerGenerated()> _
    <System.Web.Script.Services.ScriptService()> _
    Public Class com
        Inherits System.Web.Services.WebService

   &nb ...