Cannot Pass Parameters from code to Crystal Reports

This is the first time I've ever used Crystal Reports, and it shows.

In a seperate page, I select a row from a gridview and click a button to print that particular report.

The Querystring passes that value, the contract number, to the report page. 

In the rpt, I have a database field ContractNumber and have created a Crystal Reports parameter, @ContractNumber, and associated those in the record selection formula.

The associated code is:

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        Dim crystalReport As New ReportDocument()
        crystalReport.Load(Server.MapPath("FC15ContractPrint.rpt"))
        CrystalReportViewer1.ReportSource = crystalReport
        HiddenField1.Value = Request.QueryString("ContractNumber")

        Dim crParameterFieldDefinitions As ParameterFieldDefinitions
        Dim crParameterFieldDefinition As ParameterFieldDefinition
        Dim crParameterValues As New ParameterValues
        Dim crParameterDiscreteValue As New ParameterDiscreteValue

        crParameterDiscreteValue.Value = HiddenField1.Value
        crParameterFieldDefinitions = crystalReport.DataDefinition.ParameterFields()
        crParameterFieldDefinition = crParameterFieldDefinitions.Item("@ContractNumber")
        crParameterValues = crParameterFieldDefinition.CurrentValues

        crParameterValues.Clear()
        crParameterValues.Add(crParameterDiscreteValue)
        crParameterFieldDefinition.ApplyCurrentValues(crParameterValues)
        CrystalReportViewer1.RefreshReport()
    End Sub

It keeps asking me to manually input the parameter, though.