//in una classe "manager"
public static void addOnclickIfDialogFormRefreshAlways(Button btnCaller, Button btnForPostback, string strURL, string dlgHeight, string DlgWidth, string IfONclick, bool sizeable, bool maximize, bool minimize)
    {

        if (!string.IsNullOrEmpty(btnCaller.Attributes["OnClick"]))
        {

            RemoveOnClick(btnCaller);
        }


        strURL = FixUrl(strURL);

        string ScriptOpenModalDialog = "javascript: OpenModalDialog('{0}','{1}','{2}','{3}','{4}','{5}','{6}');return true;";
        btnCaller.Attributes.Add("OnClick", "if (" +IfONclick +"){"  + String.Format(ScriptOpenModalDialog, strURL, btnForPostback.ID, dlgHeight, DlgWidth, (sizeable ? "Yes" : "No"), (maximize ? "Yes" : "No"), (minimize ? "Yes" : "No")) +"}else return false;" );


    }

//nel code behind di una pagina aspx, per l'evento dataBound della griglia
protected void grdRisorse_DataBound(object sender, EventArgs e)
    {

       if (e.Row.RowType == DataControlRowType.DataRow)
        {
            Control tmpCtl = e.Row.FindControl("btnElimina");
            Control tmpTxtId = e.Row.FindControl("txtIdTipo");
            
            if (tmpCtl != null)
            {
                Button btnElimina = (Button)tmpCtl;
                if (tmpTxtId != null)
                {

                    string Id = ((TextBox)tmpTxtId).Text;
                    btnElimina.CommandArgument = Id;
                    tmpCtl = e.Row.FindControl("btnStati");
                    if (tmpCtl != null)
                    {
                        Button btnStati = (Button)tmpCtl;
                        btnStati.CommandArgument = "Id";
                        btnStati.CommandName = "btnStati";
                        string Sx = ((HiddenField)Master.FindControl("HidSession")).Value.ToString();
                        Manager.addOnclickIfDialogFormRefreshAlways(btnStati, btnStati
                                     , "~/Piani/PrevisioniAvanzamento.aspx?id=" +
                                         Id
                                        +"&Sx="+Sx 
                                          , 600.ToString()
                                          , 1250.ToString()
                                          , "checkData()"
                                          , true,true,true);

                      }
               }
       }
    }
}

//in un file .js referenziato nella pagina:
function OpenModalDialog(url, btnNameForPostback, diaHeight, diaWidth, sizeable) {
    return OpenModalDialog(url, btnNameForPostback, diaHeight, diaWidth, sizeable, "no", "no");

}
function OpenModalDialog(url, btnNameForPostback, diaHeight, diaWidth, sizeable,maximize,minimize) {
    var vReturnValue;

    if (diaHeight == null || diaHeight == "")
        diaHeight = screen.availHeight - 100;
    if (diaWidth == null || diaWidth == "")
        diaWidth = screen.availWidth - 100;


    if (url != null) {
        vReturnValue = window.showModalDialog(url, "#1", "dialogHeight: " + diaHeight + "px; dialogWidth: " + diaWidth + "px; edge: Raised; center: Yes; help: No; resizable: " + sizeable + "; status: No; maximize:" + maximize +";minimize:" + minimize );
    }
    else {
        alert("No URL passed to open");
    }
    if (vReturnValue != null && vReturnValue == true) {
       // __doPostBack(btnNameForPostback, '');
        //alert(vReturnValue);
        return vReturnValue
    }
    else {   //alert(vReturnValue);
        //alert(vReturnValue);
        return false;
    }
}