trouble with code to search db

hi
 wrote this code to search a db but when it reached the sqlconnection bit my debugger keeps bringing the NullReferenceException error.
 
 Protected Sub SearchButton_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSearch.Click

        Dim SearchString As String


        SearchString = SearchText.Text

        Dim objConnection As SqlConnection
        objConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("ConnectionString").ConnectionString)

        Dim strSQLQuery As String = "SELECT FirstName, LastName" _
        & "FROM Customer " _
        & "WHERE L ...