ASP.net: read Web.config return zero setting

Question

Using the code snippet Here

Dim appConfigs As System.Configuration.Configuration
        appConfigs = System.Web.Configuration.WebConfigurationManager.OpenWebConfiguration(Nothing)
        If (0 < appConfigs.AppSettings.Settings.Count) Then
            Dim guaranatedServiceRequestAppSetting As System.Configuration.KeyValueConfigurationElement
            guaranatedServiceRequestAppSetting = appConfigs.AppSettings.Settings("GuaranatedServiceRequestID")
            If Not (Nothing = guaranatedServiceRequestAppSetting.Value) Then
                guaranatedServiceRequestID = New Guid(guaranatedServiceRequestAppSetting.Value)
            Else
                Throw New Exception(AppResource.GuaranatedServiceRequestIDMissing)
            End If
        End If

Here is my appsetting in web.config

<appSettings>    
<add key="GuaranatedServiceRequestID" value="DF2EA0D6-62BF-4FF9-B20B-4B553134CD93" />
</appSettings>

the appConfigs.AppSettings.Settings.Count return zero. I'm not sure where i got it wrong. Can you guys help?

edit: problem solved.