Dealing with Progressive Operations

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Threading;
using Erik.Utilities.Interfaces;

namespace MultipleThreadsSample
{
    public partial class frmSearch : Form
    {
        IFindInFilesPO _po;

        EventHandler onProgressInvoker;
        EventHandler onStartInvoker;
        EventHandler onEndInvoker;
        EventHandler onAbortInvoker;
        FileFoundEventHandler onFileFoundInvoker;

        EventHandler onSubOperationStartInvoker;
        EventHandler onSubOperationEndOrAbortInvoker;

        public frmSearch()
        {
            InitializeComponent();

            Text = Program.NewTitle;

            onStartInvoker = new EventHandler(_po_OperationStart);
            onProgressInvoker = new EventHandler(_po_OperationProgress);
            onEndInvoker = new EventHandler(_po_OperationEnd);
            onAbortInvoker = new EventHandler(_po_Aborted);

            onFileFoundInvoker = new FileFoundEventHandler(_po_FileFound);

            onSubOperationStartInvoker = new EventHandler(subOperation_OperationStart);
            onSubOperationEndOrAbortInvoker = new EventHandler(subOperation_OperationEnd);
        }

        private void btnStart_Click(object sender, EventArgs e)
        {
            if (btnStart.Text == "Abort")
                _po.Abort();
            else
            {
                lstFiles.Items.Clear();
                lstFolders.Items.Clear();

                lblStatus.Text = "Preparing to search";
                ChangeControlsEnabled(false);

                Thread th = new Thread(new ThreadStart(PrepareToSearch));
                th.Start();
            }
        }

        void ChangeControlsEnabled(bool enable)
        {
            txtSearchPath.Enabled = enable;
            txtSearchText.Enabled = enable;
            btnBrowse.Enabled = enable;
            btnStart.Enabled = enable;
            chkIncludeSubFolders.Enabled = enable;
        }

        void PrepareToSearch()
        {
            if (!chkIncludeSubFolders.Checked)
                _po = new FindInFilesPO(txtSearchText.Text, txtSearchPath.Text);
            else
            {
                List<IFindInFilesPO> lst = new List<IFindInFilesPO>();
                FillOperationList(lst, txtSearchPath.Text);

                _po = new CompositeFindInFilesPO(lst, txtSearchText.Text, txtSearchPath.Text);
            }

            _po.FileFound += onFileFoundInvoker;
            _po.OperationStart += onStartInvoker;
            _po.OperationProgress += onProgressInvoker;
            _po.OperationEnd += onEndInvoker;
            _po.Aborted += onAbortInvoker;

            _po.Start();
        }

        void FillOperationList(List<IFindInFilesPO> lst, string path)
        {
            if (Directory.GetFiles(path).Length > 0)
            {
                IFindInFilesPO subOperation = new FindInFilesPO(txtSearchText.Text, path);
                lst.Add(subOperation);

                subOperation.OperationStart += onSubOperationStartInvoker;
                subOperation.OperationEnd += onSubOperationEndOrAbortInvoker;
                subOperation.Aborted += onSubOperationEndOrAbortInvoker;
            }

            string[] dirs = Directory.GetDirectories(path);
            foreach (string dir in dirs)
                FillOperationList(lst, dir);
        }

        void subOperation_OperationEnd(object sender, EventArgs e)
        {
            if (InvokeRequired)
                Invoke(onSubOperationEndOrAbortInvoker, sender, e);
            else
            {
                IFindInFilesPO po = sender as IFindInFilesPO;
                lstFolders.Items.Remove(po.SearchPath);

                pgRunningThreads.Text =
                    string.Format("Folders being processed: {0}", lstFolders.Items.Count);
            }
        }

        void subOperation_OperationStart(object sender, EventArgs e)
        {
            if (InvokeRequired)
                Invoke(onSubOperationStartInvoker, sender, e);
            else
            {
                IFindInFilesPO po = sender as IFindInFilesPO;
                lstFolders.Items.Add(po.SearchPath);

                pgRunningThreads.Text = 
                    string.Format("Folders being processed: {0}", lstFolders.Items.Count);
            }
        }

        void _po_Aborted(object sender, EventArgs e)
        {
            if (InvokeRequired)
                Invoke(onAbortInvoker, sender, e);
            else
            {
                lblStatus.Text = "Operation aborted";
                pgb.Visible = false;

                btnStart.Text = "Start";
                ChangeControlsEnabled(true);
            }
        }

        void _po_OperationEnd(object sender, EventArgs e)
        {
            if (InvokeRequired)
                Invoke(onEndInvoker, sender, e);
            else
            {
                lblStatus.Text = "Operation completed";
                btnStart.Text = "Start";
                pgb.Visible = false;

                ChangeControlsEnabled(true);
            }
        }

        void _po_OperationProgress(object sender, EventArgs e)
        {
            if (InvokeRequired)
                Invoke(onProgressInvoker, sender, e);
            else
            {
                pgb.Value = _po.CurrentProgress;
                Application.DoEvents();
            }
        }

        void _po_OperationStart(object sender, EventArgs e)
        {
            if (InvokeRequired)
                Invoke(onStartInvoker, sender, e);
            else
            {
                btnStart.Text = "Abort";
                btnStart.Enabled = true;
                pgb.Visible = true;
            }
        }

        void _po_FileFound(object sender, FileFoundEventArgs e)
        {
            if (InvokeRequired)
                Invoke(onFileFoundInvoker, sender, e);
            else
                lstFiles.Items.Add(e.FileName);
        }

        private void btnBrowse_Click(object sender, EventArgs e)
        {
            if (dlg.ShowDialog() == DialogResult.OK)
                txtSearchPath.Text = dlg.SelectedPath;
        }

        private void frmSearch_FormClosing(object sender, FormClosingEventArgs e)
        {
            try
            {
                if (_po != null)
                    _po.Abort();
            }
            catch { }
        }
    }
}