C#窗体控件阴影效果和自定义的控件如何实现阴影效果

Question

1.Win7系统小开启“窗体阴影”效果后，VS2012环境
2.无边框窗体通过SetClassLong、GetClassLongAPI可以实现窗体阴影效果。但该窗体添加至控件中时，阴影效果消失，如何能强制显示阴影效果？
3.自定义的控件如何实现阴影效果？

谢谢！

运行结果：外层窗体（Form1）有阴影效果，内层窗体(f)无阴影效果。

代码：
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();

        this.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
        //API函数加载，实现窗体边框阴影效果
        SetClassLong(this.Handle, GCL_STYLE, GetClassLong(this.Handle, GCL_STYLE) | CS_DropSHADOW);

        Form f = new Form();
        f.FormBorderStyle = System.Windows.Forms.FormBorderStyle.None;
        f.BackColor = Color.Peru;
        f.Width = 200;
        f.Height = 200;
        f.Location = new Point(50, 50); 
        f.TopLevel = false;
        this.Controls.Add(f);
        f.Show();
        SetClassLong(f.Handle, GCL_STYLE, GetClassLong(f.Handle, GCL_STYLE) | CS_DropSHADOW);
    }


    #region 窗体边框阴影效果变量申明

    const int CS_DropSHADOW = 0x20000;
    const int GCL_STYLE = (-26);
    //声明Win32 API
    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    public static extern int SetClassLong(IntPtr hwnd, int nIndex, int dwNewLong);
    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    public static extern int GetClassLong(IntPtr hwnd, int nIndex);
    #endregion
}

Answer 1

外层窗体（Form1）有阴影效果，内层窗体(f)无阴影效果。