Question

It is my first post on StackOverflow forum so please to be lenient. I have a problem with function which works called synchronously, but doesnot works called asynchronously.
Below You will find function called synchronously:

private void issueInvoices(List<int> lista)
    {
foreach (int knh_id in lista)
          {
                    Invoice fs = new Invoice();
                    fs.FKS_AKCYZA = false;
                    fs.FKS_CZY_KLON = false;
                    fs.FKS_DATE = Convert.ToDateTime(MTBDataZapisuDoFK.Text);
                    fs.NUMBER = knh_id);
         }
    }

As You can see i passed list to function named issueInvoices list of invoice numbers and in loop i create some invoices.
This function works properly but if i try to call it asynchronously (to display progress bar) my function can not assign to fs.FKS_DATE object dateTime. It looks like static function “Convert.ToDateTime” doesnot work properly. But please take a look on below code where function issueInvoices is called asynchronously…

public delegate void BinaryDelegate(List<int> knh_id);
BinaryDelegate b = new BinaryDelegate(issueInvoices);
IAsyncResult theAsRes = b.BeginInvoke(lista, new AsyncCallback(AddComplete), "Thx U!");
FrmProgressBar fpb=new FrmProgressBar(“Please wait…”);
 fpb.Show();

 /* below i check how many operation i have to do, if all operations are done, then I close fpb window, program is updating progres bar and in thread make operation issueInvoices*/
                        while (ilosc_zrobionych != liczbaKontrahentow)
                       {
                            fpb.PBStan.Value = (int)((100 * ilosc_zrobionych) / liczbaKontrahentow);
                       }
                        fpb.Close();

I put some breakpoints and it looks like program stoping in line, it can conver to datetime, but when i do this synchronously, it works without any errors.
fs.FKS_DATE = Convert.ToDateTime(MTBDataZapisuDoFK.Text);
What could couse this problem and how to resolve it?
Many thanks in advance for reply.

BELOW IS WHOLE CLASS CALLED ASYNCHRONOUSLY:

using System;
using System.Collections.Generic;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using Npgsql;
using Castle.ActiveRecord;
using WFR.Model;
using System.Threading;

namespace Faktury_i_Rachunki_2.Forms
{

    public partial class FrmEmisjaFakturPotwierdzonych : FrmBaseForm
    {

        private ArrayList listaSposobowZaplaty;
        public List<int> lista;
        private int liczbaWygenerowach;
        private int liczbaKontrahentow;
        private int ilosc_zrobionych;
        private FrmProgressBar fpb;

        public delegate void BinaryDelegate(List<int> knh_id);


        public FrmEmisjaFakturPotwierdzonych()
        {
            InitializeComponent();
    fpb = new FrmProgressBar("Please wait....");
        }

        private void BtOK_Click(object sender, EventArgs e)
        {                
                BinaryDelegate b = new BinaryDelegate(WyemitujFakture);

                    lista.Add(12);
                    lista.Add(13);
                    lista.Add(17);
                    lista.Add(1);

                liczbaKontrahentow = lista.Count;
                if (TBRejestr.Text.Trim() != "")
                {

                    if (liczbaKontrahentow > 0)
                    {
                        liczbaWygenerowach = 0;
                        ilosc_zrobionych = 0;
                        WyemitujFakture(lista);
              IAsyncResult theAsRes = b.BeginInvoke(lista, new AsyncCallback(AddComplete), "THX");

                        fpb.Show();
                        while (ilosc_zrobionych != liczbaKontrahentow)
                        {
                            fpb.PBStan.Value = (int)((100 * ilosc_zrobionych) / liczbaKontrahentow);
                        }
                        fpb.Close();
                    }

                    try
                    {
                        MessageBox.Show("Wygenerowano " + liczbaWygenerowach.ToString() + " faktur");
                    }
                    catch
                    {
}

        }
}
        private void WyemitujFakture(List<int> lista)
        {
            foreach (int knh_id in lista)
            {
                try
                {
                                    if (luk.Count > 0)
                    {
                        FakturySprzedazy fs = new FakturySprzedazy();
                        fs.FKS_AKCYZA = false;
                        fs.FKS_CZY_KLON = false;
                        fs.FKS_DATA_DOW_KS = Convert.ToDateTime(MTBDataZapisuDoFK.Text);
                        fs.FKS_DATA_FAKTURY = Convert.ToDateTime(MTBDataFaktury.Text);
                        fs.FKS_DATA_SPRZEDAZY = Convert.ToDateTime(MTBDataSprzedazy.Text);
                        liczbaWygenerowach++;
                    }

                }
                catch (Exception ex)
                {
                    MessageBox.Show("Nie można wyemitować faktury dla kontrahenta o id = " + knh_id.ToString() + " " + ex.Message);
                }
                ilosc_zrobionych++;
            }
        }

Answer 1

The problem is in getting the value of MTBDataZapisuDoFK.Text (which I assume to be a textbox). Getting or setting the text of a textbox means sending messages to its window. But you keep the UI-thread busy in the while loop and therefore it can not process any messages.

Put a call to Application.DoEvents() into the while loop to allow messages to be processed:

fpb.Show();
while (ilosc_zrobionych != liczbaKontrahentow)
{
    Application.DoEvents();
    fpb.PBStan.Value = (int)((100 * ilosc_zrobionych) / liczbaKontrahentow);
}
fpb.Close();

I assume that the only reason for calling the method asynchronously is to be able to update the UI during processing the WyemitujFakture-method. Using Application.DoEvents() you do not need asynchonous calls:

fpb = new FrmProgressBar("Please wait....");
fpb.Show();
Application.DoEvents();
WyemitujFakture(lista);
fpb.Close();

You should call Application.DoEvents() after you call fpb.Show() to allow the form to be displayed properly. Also you should instantiate the form in the method itself instead of the constructor, because you can not use the same instance again after calling fpb.Close() (it will be disposed).

Then you can update the progress bar in the WyemitujFakture-method:

private void WyemitujFakture(List<int> lista)
{
    foreach (int knh_id in lista)
    {
        try
        {
            if (luk.Count > 0)
            {
                FakturySprzedazy fs = new FakturySprzedazy();
                fs.FKS_AKCYZA = false;
                fs.FKS_CZY_KLON = false;
                fs.FKS_DATA_DOW_KS = Convert.ToDateTime(MTBDataZapisuDoFK.Text);
                fs.FKS_DATA_FAKTURY = Convert.ToDateTime(MTBDataFaktury.Text);
                fs.FKS_DATA_SPRZEDAZY = Convert.ToDateTime(MTBDataSprzedazy.Text);
                liczbaWygenerowach++;
            }

        }
        catch (Exception ex)
        {
            MessageBox.Show("Nie mozna wyemitowac faktury dla kontrahenta o id = " + knh_id.ToString() + " " + ex.Message);
        }
        ilosc_zrobionych++;

        fpb.PBStan.Value = (int)((100 * ilosc_zrobionych) / liczbaKontrahentow);
        Application.DoEvents();
    }
}