Question

how can i do this client side,
OnClientClick of the btnYes will return false if the gridview selected index < 0;

protected void btnYes_Click(object sender, EventArgs e)
{
    if (gvCourseDetails.SelectedIndex == -1)
    {
        ClientScriptManager scriptManager = Page.ClientScript;
        scriptManager.RegisterClientScriptBlock(this.GetType(), "alertmessage",
                       "<script>alert('Select a course above first');</script>");
    }
}

Thanks.

Answer 1

The GridView’s selected index will not change without a postback anyway, so you can evaluate it only once on the server side (on page_load or btnYes prerender, etc). It is almost meaningless on the client side.

if (gvCourseDetails.SelectedIndex == -1)
{
   btnYes.OnClientClick = "alert('Select a course above first'); return false;";
}
else
{
   btnYes.OnClientClick = "";
}