C# Form内存回收

namespace WebBrowserMemoryTest
{
    public partial class Form1 : Form
    {
        private int _Pages;

        public Form1()
        {
            InitializeComponent();
            webBrowser1.Navigate("http://www.google.com");
        }

        private void startButton_Click(object sender, EventArgs e)
        {
            _Pages = 0;
            timer1.Start();
        }

        private void stopButton_Click(object sender, EventArgs e)
        {
            timer1.Stop();
        }

        private void timer1_Tick(object sender, EventArgs e)
        {
            HtmlElement next = webBrowser1.Document.GetElementById("pnnext");

            if (_Pages <= 90)
            {
                if (null != next)
                {
                    string href = next.GetAttribute("href");
                    webBrowser1.Navigate(href);
                    _Pages++;
                }
                else
                {
                    timer1.Stop();
                    MessageBox.Show("Next button not found");
                }
            }
            else
            {
                timer1.Stop();
                MessageBox.Show("Done");
            }
        }

        private void goButton_Click(object sender, EventArgs e)
        {
            webBrowser1.Navigate(textBox1.Text);
        }

        private void freeMemButton_Click(object sender, EventArgs e)
        {
            MemoryManagement.FlushMemory();
        }
    }

    public class MemoryManagement
    {
        [DllImport("kernel32.dll")]
        public static extern bool SetProcessWorkingSetSize(IntPtr proc, int min, int max);

        public static void FlushMemory()
        {
            GC.Collect();
            GC.WaitForPendingFinalizers();
            if (Environment.OSVersion.Platform == PlatformID.Win32NT)
            {
                SetProcessWorkingSetSize(System.Diagnostics.Process.GetCurrentProcess().Handle, -1, -1);
            }
        }
    }
}