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namespace Webbrowser
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            this.StartPosition = FormStartPosition.Manual;
            this.Location = new Point(-5, 0);
            SHDocVw.WebBrowser_V1 axBrowser = (SHDocVw.WebBrowser_V1)webBrowser1.ActiveXInstance;
            axBrowser.NewWindow += axBrowser_NewWindow;
        }
        
        void axBrowser_NewWindow(string URL, int Flags, string TargetFrameName, ref object PostData, string Headers, ref bool Processed)
        {
            Processed = true;
            webBrowser1.Navigate(URL);
            ClosePrintDlg();
        }

        [System.Runtime.InteropServices.DllImport("User32.dll")]
        static extern int FindWindow(string lpClassName, string lpWindowName);

        [System.Runtime.InteropServices.DllImport("User32.dll")]
        static extern int SendMessage(int hWnd, uint Msg, int wParam, int lParam);

        const int WM_SYSCOMMAND = 0x0112;
        const int SC_CLOSE = 0xF060;

        private void CloseWindow(string className, string windowName)
        {
            int windowHandle = FindWindow(className, windowName);
            if (windowHandle != 0)
                SendMessage(windowHandle, WM_SYSCOMMAND, SC_CLOSE, 0);
        }

        const string PRINTDLG_CLASS = "#32770";
        const string PRINTDLG_WINDOW = "Drucken";

        private void ClosePrintDlg()
        {
            CloseWindow(PRINTDLG_CLASS, PRINTDLG_WINDOW);
        }
    }
}                    

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private async Task ClosePrintDialog()
{
    const string PRINTDLG_CLASS = "#32770";
    const string PRINTDLG_WINDOW = "Drucken";
    const int WM_SYSCOMMAND = 0x0112;
    const int SC_CLOSE = 0xF060;

    int printDialogWindowHandle;

    do
    {
        printDialogWindowHandle = FindWindow(PRINTDLG_CLASS, PRINTDLG_WINDOW);
        await Task.Delay(10);
    } while (printDialogWindowHandle == 0);

    SendMessage(printDialogWindowHandle, WM_SYSCOMMAND, SC_CLOSE, 0);
    ClosePrintDialogTimer.Stop();
}

[DllImport("User32.dll")]
static extern int FindWindow(string lpClassName, string lpWindowName);

[DllImport("User32.dll")]
static extern int SendMessage(int hWnd, uint Msg, int wParam, int lParam);