Populating text boxes with list box selected index?

FileOpen(1, CustomerInfo, OpenMode.Random, , , Len(Customer))

        Do While Not EOF(1)
            FileGet(1, Customer)

            Dim SearchString As String = lstSearch.SelectedItems.ToString

            If Customer.CustomerUniqueID = SearchString.Contains(Customer.CustomerUniqueID) = True Then

                frmBookings.txtCustomerForename.Text = Customer.CustomerForename
                frmBookings.txtCustomerID.Text = Customer.CustomerUniqueID
                frmBookings.txtCustomerSurname.Text = Customer.CustomerSurname
                frmBookings.txtCustomerDOB.Text = Customer.CustomerDOB

                Exit Do
            End If
        Loop

        FileClose(1)

I'm losing my rag a little, I want to populate text boxes on a separate form but so far I've had no luck. How I'm going about doing so is trying to compare a selected index against a field in a record. If the selected index contains a text item matching the field in the if selection then the text boxes would be filled with information related to the matching record it came from. But I've got an error message saying "Conversion from string "LaneCal10 " to type 'Boolean' is not valid." LANECal10 being the unique customerID.

Any help?