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);
}
}
}
}