How to get values from asp.net gridview cell on linkbutton click

Hi

I want take value from gridview when Linkbutton from gridview cliked 

on link button clicked event 

my code is 

    Protected Sub LinkStudentID_Click(ByVal sender As Object, ByVal e As EventArgs) 

ModalPopupExtender1.Show()

            Dim Val_StudentID As String = ""

            Dim Val_class As String = ""

            Dim linkbtn As LinkButton = DirectCast(sender, LinkButton)

            'Get the row that contains this button

            Dim gvr As GridViewRow = DirectCast(linkbtn.NamingContainer, GridViewRow)

            'Get rowindex

            Dim rowindex As Integer = gvr.RowIndex

            Val_StudentID = CType(StudentGridview.Rows(rowindex).Cells(1).Text, String)

            Val_class = CType(StudentGridview.Rows(rowindex).Cells(6).Text, String)

           studentid.Text = Val_StudentID 

          class.Text = Val_class 

           end sub