C#

public int SetSite(object site)
        {
            SHDocVw.IWebBrowser2 m_pIWebBrowser2 = site as SHDocVw.IWebBrowser2;
            IServiceProvider ISP = site as IServiceProvider;

            if (m_pIWebBrowser2 != null)
            {
                Marshal.ReleaseComObject(m_pIWebBrowser2);
                m_pIWebBrowser2 = null;
            }

            if (Explorer != null)
            {
                Marshal.ReleaseComObject(Explorer);
                Explorer = null;
            }

            if (ISP != null)
            {
                Guid IID_IUnknown = new
                Guid("{00000000-0000-0000-C000-000000000046}");
                Guid IID_IWebBrowserApp = new
                Guid("{0002DF05-0000-0000-C000-00000000046}");
                object pOut;

                try
                {
                    ISP.QueryService(ref IID_IWebBrowserApp, ref IID_IUnknown, out
                    pOut);
                    Explorer = (WebBrowserClass)Marshal.CreateWrapperOfType(pOut as
                    IWebBrowser2, typeof(WebBrowserClass));
                }
                catch (Exception e)
                {
                    System.Windows.Forms.MessageBox.Show(e.Message, "Talkative Browser");
                }
            }

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public struct OLECMDTEXT
    {
        public uint cmdtextf;
        public uint cwActual;
        public uint cwBuf;
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 100)]
        public char rgwz;
    }


    [StructLayout(LayoutKind.Sequential)]
    public struct OLECMD
    {
        public uint cmdID;
        public uint cmdf;
    }


    [ComImport,
    Guid("b722bccb-4e68-101b-a2bc-00aa00404770"),
    InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IOleCommandTarget
    {
        void QueryStatus(ref Guid pguidCmdGroup, UInt32 cCmds,
        [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)] OLECMD[] prgCmds, ref 
        OLECMDTEXT CmdText);
        void Exec(ref Guid pguidCmdGroup, uint nCmdId, uint nCmdExecOpt, ref object
        pvaIn, ref object pvaOut);
    }

try
     {
        using (StreamWriter writer = File.CreateText(path))
        {
            foreach (string line in rich.Lines)
                   writer.WriteLine(line);
        }
     }
     catch (IOException e)
     {
         // error handling here
     }

 private void button1_Click(object sender, EventArgs e)
        {
// for getting the items ToLower case
            string[] fajli = Directory.GetFiles(Application.StartupPath,"*.*",SearchOption.AllDirectories);
            string[] VsiFajli = Array.ConvertAll<string,>(fajli, delegate(string s) { return s.ToLower(); });

            listBox1.Items.AddRange(VsiFajli);

            for (int i = 0; i < listBox1.Items.Count; i++)
            {
                // checks if the file is .pdf
                if (listBox1.Items[i].ToString() == listBox1.Items[i].ToString().Remove(listBox1.Items[i].ToString().Length - 4, 4) + ".pdf")
                {
                    if (File.Exists(listBox1.Items[i].ToString().Remove(listBox1.Items[i].ToString().Length - 4,4) + "_1.pdf"))
                    {
                        string temp = listBox1.Items[i].ToString();
                        
                        listBox1.Items.Remove(temp);
                        listBox1.Items.Remove(temp.Remove(temp.Length - 4,4) + "_1.pdf");


                        //listBox1.Items.RemoveAt(i);
                    }
                }
                else // if its not pdf ...
                {
                    if (File.Exists(listBox1.Items[i].ToString().Remove(listBox1.Items[i].ToString().Length - 4,4) + ".pdf"))
                    {
                        string temp = listBox1.Items[i].ToString();
                        listBox1.Items.Remove(temp);
                        listBox1.Items.Remove(temp.Remove(temp.Length - 4,4) + ".pdf");
                        listBox1.Items.Remove(temp.Remove(temp.Length - 4, 4) + "_1.pdf");


                        //listBox1.Items.RemoveAt(i);
                    }
                }
            }
            MessageBox.Show("Done!");
        }

        private void listBox1_DoubleClick(object sender, EventArgs e)
        {
            if(listBox1.SelectedItem!=null)
            System.Diagnostics.Process.Start(listBox1.SelectedItem.ToString());
        }

        private void button2_Click(object sender, EventArgs e)
        {
// for removing all .gif items
            if(listBox1.Items.Count != 0)
            for (int j = 0; j < listBox1.Items.Count; j++)
            {
                if(listBox1.Items[j].ToString() == (listBox1.Items[j].ToString().Remove(listBox1.Items[j].ToString().Length-4,4) + ".gif"))
                    listBox1.Items.RemoveAt(j);
            }
        }

        private void button3_Click(object sender, EventArgs e)
        {
// copying the selected item to clipboard.
            if (listBox1.SelectedItem != null)
                Clipboard.SetText(listBox1.SelectedItem.ToString()) ;
        }