Try this
Html Code Default.aspx
<asp:GridView ID="gvDetails" runat="server" AutoGenerateColumns="False" DataSourceID="sqlDataSource">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:LinkButton ID="lnkUpdate" runat="server" Text="Update" ToolTip='<%#Eval("CustomerID") %>'
CommandName="Update"></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField>
<ItemTemplate>
<asp:LinkButton ID="lnkView" runat="server" Text="View" ToolTip='<%#Eval("CustomerID") %>'
CommandName="View"></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
<asp:BoundField DataField="CustomerID" HeaderText="CustomerID" SortExpression="CustomerID" />
<asp:BoundField DataField="Title" HeaderText="Title" SortExpression="Title" />
</Columns>
</asp:GridView>
<asp:SqlDataSource ID="sqlDataSource" runat="server" ConnectionString="<%$ ConnectionStrings:ConnectionString %>"
ProviderName="<%$ ConnectionStrings:ConnectionString.ProviderName %>" SelectCommand="SELECT [CustomerID], [Title] FROM [Contacts]">
</asp:SqlDataSource>
Code
Protected Sub gvDetails_RowCommand(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.GridViewCommandEventArgs) Handles gvDetails.RowCommand
Dim lblReferenceNo As LinkButton
Dim referenceNo As String
lblReferenceNo = TryCast(e.CommandSource, LinkButton)
referenceNo = lblReferenceNo.ToolTip.ToString()
Session("REF") = referenceNo
If e.CommandName = "Update" Then
Response.Redirect("~/Update.aspx")
End If
If e.CommandName = "View" Then
Response.Redirect("~/View.aspx")
End If
End Sub
Update.aspx Code
txtUpdate.Text = Convert.ToString(Session("REF"))
View.aspx Code
txtView.Text = Convert.ToString(Session("REF"))