Gridview checkbox problem

Question

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I am taking check box in gridview follwing and more data coming from database

how can i get each and every cell value of that checked box checked row

i have tried like this
but getting null in string

Dim chkbox As CheckBox = CType(sender, CheckBox)
Dim Grow As GridViewRow = CType(chkbox.NamingContainer, GridViewRow)

If chkbox.Checked = True Then

Dim completed_value As String = "True"

Dim calluid As String = Grow.Cells(2).Text

Dim salesrep As String = Grow.Cells(2).Text

Dim coname As String = Grow.Cells(3).Text

Dim salesdate As String = Grow.Cells(4).Text

Dim salesnote As String = Grow.Cells(5).Text

End If
asp:TemplateField HeaderText="xxx">
<ItemTemplate><asp:CheckBox ID="check" runat="server" OnCheckedChanged="check_CheckedChanged" AutoPostBack="true"></asp:CheckBox></ItemTemplate></asp:TemplateField>