thanks, a small step forward.

Get CommandArgument property value of ASP.Net ImageButton in C#

Now the value of the CommandArgument from recovery button is right.

protected void btnReco_Click(object sender, ImageClickEventArgs e)
{
    int t = Convert.ToInt32((sender as ImageButton).CommandArgument);
    //Response.Write(t.ToString() + "<br />"); Response.End();
    
 
    switch (t)
    {
        case 1:
            gvProducts.DataSource = RetrieveProducts_reco();
            gvProducts.DataBind();
    }
}

But how to do a populated the dropdownlist with the value stored in database, in RowDataBound, if use the recovery button?