Winform 关闭窗口后如何清理内存？

打开 Winform 窗口后，内存一直增加，关闭窗口后，内存不会还原，使用Dispose();没有效果

比如第一段代码中使用 Winform 显示图片

另外找到 .NET API 中，GC.Collect();和SetProcessWorkingSetSize函数，会降低内存显示，实际上是转移到虚拟内存中，效果非常不好

是否有好的办法关闭 form 窗口后，清理内存的呢

var Forms = forms.System.Windows.Forms;
var form = new Forms.Form;
form.StartPosition = Forms.FormStartPosition.Manual;
form.FormBorderStyle = Forms.FormBorderStyle.None;
form.TopMost = true;
form.ControlBox = false;
form.ShowInTaskbar = false;
form.Margin = new Forms.Padding(0);
form.Padding = new Forms.Padding(1);
form.MinimumSize = new Size(10, 10);
form.Size = new Size(10, 10);
form.Location = new Point(100, 100);
form.AutoSize = true;
form.GetType().GetProperty("DoubleBuffered",
    host.flags(clr.System.Reflection.BindingFlags.NonPublic,
    clr.System.Reflection.BindingFlags.Instance))
    .SetValue(form, true);
form.BackColor = drawing.System.Drawing.SystemColors.HotTrack;

var pic = new Forms.PictureBox;
pic.Name = 'pic';
pic.SizeMode = Forms.PictureBoxSizeMode.Zoom;
pic.Size = new Size(450, 500);
pic.BackColor = drawing.System.Drawing.SystemColors.Control;
pic.Location = new Point(0, 0);
pic.Image = img;

form.Controls.Add(pic);
var autoSize = form.Size;
var t = (form.ClientSize.Width - pic.Width - form.Padding.Horizontal);
autoSize.Width -= t;
autoSize.Height -= t;
form.AutoSize = false;
form.Size = autoSize;
pic.Dock = Forms.DockStyle.Fill;

var form_shown = 
form.Shown.connect(
function (sender, args) {
    form.TopMost = true;
    form.Activate();
});

var pic_doubleClick = 
pic.DoubleClick.connect(
function (sender, args) {
    form.Dispose();
    pic.Dispose();
    Forms.Application.Exit();
    form.Close(); 
});

Forms.Application.Run(form);
img.Dispose();

使用SetProcessWorkingSetSize

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