ConfigurationManager.ConnectionStrings: Object reference not set to an instance of an object.

Dear All

Hope all you are fine

i want to show CR through dataset. I have visit your page

http://www.aspsnippets.com/Articles/Crystal-Report-ASPNet-Example-using-DataSet-or-DataTable-in-C-VBNet-and-Visual-Studio-2010.aspx#

I download your demo

when i run error comes 

Object reference not set to an instance of an object.

 here is my code

 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("~/crpt.rpt"))
        Dim dsCustomers As DataSet1 = GetData("select * from tblTest")
        crystalReport.SetDataSource(dsCustomers)
        CrystalReportViewer1.ReportSource = crystalReport
    End Sub
    Private Function GetData(ByVal query As String) As DataSet1
        Dim conString As String = ConfigurationManager.ConnectionStrings("Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\Database.mdf;Integrated Security=True;User Instance=True").ConnectionString
        Dim cmd As New SqlCommand(query)
        Using con As New SqlConnection(conString)
            Using sda As New SqlDataAdapter()
                cmd.Connection = con

                sda.SelectCommand = cmd
                Using dsCustomers As New DataSet1()
                    sda.Fill(dsCustomers, "tblTest")
                    Return dsCustomers
                End Using
            End Using
        End Using
    End Function

please help thanks