Этот код работал для меня:
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Dim intr As IWc fInterface
Dim chnl As ChannelFactory(Of IWcfInterface) = New ChannelFactory(Of IWcfInterface)(New WebHttpBinding(), "http://localhost:49821/Service1.svc")
chnl.Endpoint.Behaviors.Add(New WebHttpBehavior())
intr = chnl.CreateChannel()
Using New OperationContextScope(DirectCast(intr, IContextChannel))
Dim rspnse As List(Of UserDetails) = intr.GetDataFromDB()
GridView1.DataSource = rspnse
GridView1.DataBind()
End Using
End Sub