using  System.Drawing.Drawing2D;

override protected void OnPaintBackground(PaintEventArgs e)
{
   LinearGradientBrush brush =
   new System.Drawing.Drawing2D.LinearGradientBrush(ClientRectangle, Color.Red, Color.White, 0f);
   e.Graphics.FillRectangle(brush, ClientRectangle);
}

Komunikaty windows:

WM_NULL = 0x00
WM_CREATE = 0x01
WM_DESTROY = 0x02
WM_MOVE = 0x03
WM_SIZE = 0x05
WM_ACTIVATE = 0x06
WM_SETFOCUS = 0x07
WM_KILLFOCUS = 0x08
WM_ENABLE = 0x0A
WM_SETREDRAW = 0x0B
WM_SETTEXT = 0x0C
WM_GETTEXT = 0x0D
WM_GETTEXTLENGTH = 0x0E
WM_PAINT = 0x0F
WM_CLOSE = 0x10
WM_QUERYENDSESSION = 0x11
WM_QUIT = 0x12
WM_QUERYOPEN = 0x13
WM_ERASEBKGND = 0x14
WM_SYSCOLORCHANGE = 0x15
WM_ENDSESSION = 0x16
WM_SYSTEMERROR = 0x17
WM_SHOWWINDOW = 0x18
WM_CTLCOLOR = 0x19
WM_WININICHANGE = 0x1A
WM_SETTINGCHANGE = 0x1A
WM_DEVMODECHANGE = 0x1B
WM_ACTIVATEAPP = 0x1C
WM_FONTCHANGE = 0x1D
WM_TIMECHANGE = 0x1E
WM_CANCELMODE = 0x1F
WM_SETCURSOR = 0x20
WM_MOUSEACTIVATE = 0x21
WM_CHILDACTIVATE = 0x22
WM_QUEUESYNC = 0x23
WM_GETMINMAXINFO = 0x24
WM_PAINTICON = 0x26
WM_ICONERASEBKGND = 0x27
WM_NEXTDLGCTL = 0x28
WM_SPOOLERSTATUS = 0x2A
WM_DRAWITEM = 0x2B
WM_MEASUREITEM = 0x2C
WM_DELETEITEM = 0x2D
WM_VKEYTOITEM = 0x2E
WM_CHARTOITEM = 0x2F

WM_SETFONT = 0x30
WM_GETFONT = 0x31
WM_SETHOTKEY = 0x32
WM_GETHOTKEY = 0x33
WM_QUERYDRAGICON = 0x37
WM_COMPAREITEM = 0x39
WM_COMPACTING = 0x41
WM_WINDOWPOSCHANGING = 0x46
WM_WINDOWPOSCHANGED = 0x47
WM_POWER = 0x48
WM_COPYDATA = 0x4A
WM_CANCELJOURNAL = 0x4B
WM_NOTIFY = 0x4E
WM_INPUTLANGCHANGEREQUEST = 0x50
WM_INPUTLANGCHANGE = 0x51
WM_TCARD = 0x52
WM_HELP = 0x53
WM_USERCHANGED = 0x54
WM_NOTIFYFORMAT = 0x55
WM_CONTEXTMENU = 0x7B
WM_STYLECHANGING = 0x7C
WM_STYLECHANGED = 0x7D
WM_DISPLAYCHANGE = 0x7E
WM_GETICON = 0x7F
WM_SETICON = 0x80

WM_NCCREATE = 0x81
WM_NCDESTROY = 0x82
WM_NCCALCSIZE = 0x83
WM_NCHITTEST = 0x84
WM_NCPAINT = 0x85
WM_NCACTIVATE = 0x86
WM_GETDLGCODE = 0x87
WM_NCMOUSEMOVE = 0xA0
WM_NCLBUTTONDOWN = 0xA1
WM_NCLBUTTONUP = 0xA2
WM_NCLBUTTONDBLCLK = 0xA3
WM_NCRBUTTONDOWN = 0xA4
WM_NCRBUTTONUP = 0xA5
WM_NCRBUTTONDBLCLK = 0xA6
WM_NCMBUTTONDOWN = 0xA7
WM_NCMBUTTONUP = 0xA8
WM_NCMBUTTONDBLCLK = 0xA9

WM_KEYFIRST = 0x100
WM_KEYDOWN = 0x100
WM_KEYUP = 0x101
WM_CHAR = 0x102
WM_DEADCHAR = 0x103
WM_SYSKEYDOWN = 0x104
WM_SYSKEYUP = 0x105
WM_SYSCHAR = 0x106
WM_SYSDEADCHAR = 0x107
WM_KEYLAST = 0x108

WM_IME_STARTCOMPOSITION = 0x10D
WM_IME_ENDCOMPOSITION = 0x10E
WM_IME_COMPOSITION = 0x10F
WM_IME_KEYLAST = 0x10F

WM_INITDIALOG = 0x110
WM_COMMAND = 0x111
WM_SYSCOMMAND = 0x112
WM_TIMER = 0x113
WM_HSCROLL = 0x114
WM_VSCROLL = 0x115
WM_INITMENU = 0x116
WM_INITMENUPOPUP = 0x117
WM_MENUSELECT = 0x11F
WM_MENUCHAR = 0x120
WM_ENTERIDLE = 0x121

WM_CTLCOLORMSGBOX = 0x132
WM_CTLCOLOREDIT = 0x133
WM_CTLCOLORLISTBOX = 0x134
WM_CTLCOLORBTN = 0x135
WM_CTLCOLORDLG = 0x136
WM_CTLCOLORSCROLLBAR = 0x137
WM_CTLCOLORSTATIC = 0x138

WM_MOUSEFIRST = 0x200
WM_MOUSEMOVE = 0x200
WM_LBUTTONDOWN = 0x201
WM_LBUTTONUP = 0x202
WM_LBUTTONDBLCLK = 0x203
WM_RBUTTONDOWN = 0x204
WM_RBUTTONUP = 0x205
WM_RBUTTONDBLCLK = 0x206
WM_MBUTTONDOWN = 0x207
WM_MBUTTONUP = 0x208
WM_MBUTTONDBLCLK = 0x209
WM_MOUSEWHEEL = 0x20A
WM_MOUSEHWHEEL = 0x20E

WM_PARENTNOTIFY = 0x210
WM_ENTERMENULOOP = 0x211
WM_EXITMENULOOP = 0x212
WM_NEXTMENU = 0x213
WM_SIZING = 0x214
WM_CAPTURECHANGED = 0x215
WM_MOVING = 0x216
WM_POWERBROADCAST = 0x218
WM_DEVICECHANGE = 0x219

WM_MDICREATE = 0x220
WM_MDIDESTROY = 0x221
WM_MDIACTIVATE = 0x222
WM_MDIRESTORE = 0x223
WM_MDINEXT = 0x224
WM_MDIMAXIMIZE = 0x225
WM_MDITILE = 0x226
WM_MDICASCADE = 0x227
WM_MDIICONARRANGE = 0x228
WM_MDIGETACTIVE = 0x229
WM_MDISETMENU = 0x230
WM_ENTERSIZEMOVE = 0x231
WM_EXITSIZEMOVE = 0x232
WM_DROPFILES = 0x233
WM_MDIREFRESHMENU = 0x234

WM_IME_SETCONTEXT = 0x281
WM_IME_NOTIFY = 0x282
WM_IME_CONTROL = 0x283
WM_IME_COMPOSITIONFULL = 0x284
WM_IME_SELECT = 0x285
WM_IME_CHAR = 0x286
WM_IME_KEYDOWN = 0x290
WM_IME_KEYUP = 0x291

WM_MOUSEHOVER = 0x2A1
WM_NCMOUSELEAVE = 0x2A2
WM_MOUSELEAVE = 0x2A3

WM_CUT = 0x300
WM_COPY = 0x301
WM_PASTE = 0x302
WM_CLEAR = 0x303
WM_UNDO = 0x304

WM_RENDERFORMAT = 0x305
WM_RENDERALLFORMATS = 0x306
WM_DESTROYCLIPBOARD = 0x307
WM_DRAWCLIPBOARD = 0x308
WM_PAINTCLIPBOARD = 0x309
WM_VSCROLLCLIPBOARD = 0x30A
WM_SIZECLIPBOARD = 0x30B
WM_ASKCBFORMATNAME = 0x30C
WM_CHANGECBCHAIN = 0x30D
WM_HSCROLLCLIPBOARD = 0x30E
WM_QUERYNEWPALETTE = 0x30F
WM_PALETTEISCHANGING = 0x310
WM_PALETTECHANGED = 0x311

WM_HOTKEY = 0x312
WM_PRINT = 0x317
WM_PRINTCLIENT = 0x318

WM_HANDHELDFIRST = 0x358
WM_HANDHELDLAST = 0x35F
WM_PENWINFIRST = 0x380
WM_PENWINLAST = 0x38F
WM_COALESCE_FIRST = 0x390
WM_COALESCE_LAST = 0x39F
WM_DDE_FIRST = 0x3E0
WM_DDE_INITIATE = 0x3E0
WM_DDE_TERMINATE = 0x3E1
WM_DDE_ADVISE = 0x3E2
WM_DDE_UNADVISE = 0x3E3
WM_DDE_ACK = 0x3E4
WM_DDE_DATA = 0x3E5
WM_DDE_REQUEST = 0x3E6
WM_DDE_POKE = 0x3E7
WM_DDE_EXECUTE = 0x3E8
WM_DDE_LAST = 0x3E8

WM_USER = 0x400
WM_APP = 0x8000

…zacząłem szukać w google…

…i zdruzgotany nic nie znalazłem – poza – kilkoma poradami, aby wprowadzić własną obsługę za pomocą Timera i MouseDown/MouseUp. Do bani.

A rozwiązanie istnieje i jest ono całkiem eleganckie. Należy utworzyć własną kontrolkę rozszerzającą ListView, a następnie nadpisać metodę

protected override void WndProc(ref Message m)

takim kawałkem kodu:

if (m.Msg == 0×203) //WM_LBUTTONDBLCLK
{
this.OnDoubleClick(MouseEventArgs.Empty);
}
else
{
base.WndProc(ref m);
}

I już. Przechwytujemy wszystkie komunikaty i w przypadku gdy jest to podwójne kliknięcie, wywołujemy zawsze zdarzenie OnDoubleClick. Podobnie można zrobić dla pojedynczego kliknięcia, tylko sobie ustalcie ID komunikatu.

using System.Net;
 
namespace DownloadTest
{
    class Program
    {
        static void Main(string[] args)
        {
            WebClient webClient = new WebClient();
            try
            {
                webClient.DownloadFile("http://server/file", "myFileName");
            }
            catch (WebException e)
            {
                //some error
            }
        }
    }
}

Metoda DownloadFile z klasy webClient przyjmuje dwa parametry: String lub URI z adresem sieciowym pliku oraz String z nazwą pod jaką plik zostanie zapisany lokalnie. Jednak ta metoda jest częściowo nieelegancka – blokuje całkowicie wątek aż do zakończenia pobierania pliku. Nie możemy w tym czasie odebrać żadnych eventów (np. użytkownik nie będzie w stanie przerwać operacji ściągania) ani np. informować o postępie. Zamiast niej możemy jednak użyć podobnej metody – DownloadFileAsync(Uri, String):

using System;
using System.Net;
 
namespace DownloadTest
{
    class Program
    {
        static void Main(string[] args)
        {
            WebClient webClient = new WebClient();
 
            webClient.DownloadFileCompleted += new System.ComponentModel.AsyncCompletedEventHandler(webClient_DownloadFileCompleted);
            webClient.DownloadProgressChanged += new DownloadProgressChangedEventHandler(webClient_DownloadProgressChanged);
 
            try
            {
                webClient.DownloadFileAsync(new Uri("http://server/file"), "myFileName");
            }
            catch (WebException e)
            {
                //stało się coś bardzo niedobrego ;)
            }
        }
 
        static void webClient_DownloadProgressChanged(object sender, DownloadProgressChangedEventArgs e)
        {
            //zobaczmy ile procent pobrano: 
            Console.WriteLine(e.ProgressPercentage.ToString());
        }
 
        static void webClient_DownloadFileCompleted(object sender, System.ComponentModel.AsyncCompletedEventArgs e)
        {
            //zakończono pobieranie pliku
        }
    }
}

Warto zapamiętać, że za pomocą DownloadFileAsync nie możemy w jednym wątku ściągać jednocześnie więcej niż jednego pliku – w przypadku próby dokonania takiej operacji otrzymamy wyjątek. Dlatego z pobieraniem kolejnego pliku musimy poczekać do zakończenia pobierania poprzedniego.