Question

This should be fairly basic, but say I have a Public property as local variable on my WCF service, and I set this in one call to the service. Is there a way to preserve that data for another call to the service? (Without writing the data to xml or a db, and re-referencing it or anything like that)

Executing the calls from the Winform:

Public Class ClientSideWinForm

    Private proxy As ServiceReference.Client

    Private Sub Client_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        proxy = New ServiceReference.Client
    End Sub

    Private Sub btnStartTests_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnStartTests.Click
        addToTxtResults("Try Chk Program Valid...")
        Try
            addToTxtResults(proxy.RequestChkValidProgram("Some-serial-number")) 'returns true or false and instanciates the object server side

            addToTxtResults(proxy.RequestFirstName()) ' returns nothing
        Catch ex As Exception
            addToTxtResults(ex.ToString)
        End Try
    End Sub
End Class

The service itself (dumbed down a bit, but the behaivor still exists):

Public Class Service
    Implements IService

Public Property X As String

Function RequestChkValidProgram(ByVal strSerialNumber As String) As Integer Implements IService.RequestChkValidProgram
        X = "hello"
End Function

Function RequestFirstName() As String Implements IService.RequestFirstName
    Return X
End Function

End Class

Answer 1

If I understand the question correctly, your service implementation’s state is lost between service calls. You should look into setting the InstanceContextMode ServiceBehavior of your service implementation – it sounds like it’s currently set to PerCall, such that every service call gets its own instance. PerSession or Single may be better alternatives.

And while I don’t necessarily agree with @John Saunders that this is a bad idea, it would be useful to have more details about what you’re trying to accomplish. 🙂