Try this,
Modify Checkbox in Gridview like,
<asp:TemplateField HeaderText="View">
<ItemTemplate>
<asp:CheckBox ID="chkview" runat="server" AutoPostBack="true" OnCheckedChanged="chkview_CheckedChanged" />
</ItemTemplate>
</asp:TemplateField>
And on Code view define,
protected void chkview_CheckedChanged(object sender, EventArgs e)
{
}