secure.asmx

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<%@ WebService Class="SecureSample" %>

Imports System.Web.Services
Imports System.Web.Security

Public Class SecureSample
  Inherits WebService

  <WebMethod> _
  Public Function WhoAreYou() As String
    Return User.Identity.Name
  End Function

  <WebMethod> _
  Public Function Authenticate(username As String, password As String)
    If (username = "John") AND (password = "password") Then
      FormsAuthentication.SetAuthCookie(username, true)
      
      Return true
    End If

    Return false
  End Function
End Class