<转载>C# 通过API改变窗体形状

using System.Runtime.InteropServices;

[DllImportAttribute ("gdi32.dll")] 
public static extern IntPtr CreateRoundRectRgn(int nLeftRect,int nTopRect,int nRightRect,int nBottomRect,int nWidthEllipse,int nHeightEllipse);   
[DllImportAttribute ("user32.dll")]   
public static extern int SetWindowRgn(IntPtr hWnd,IntPtr hRgn, bool bRedraw); 

Fom1 fl = new Form1();
IntPtr regionHandle =CreateRoundRectRgn(0,0,fl.Width,fl.Height,20,20); 
Region roundRegion = null; 
roundRegion = Region.FromHrgn(regionHandle); 
SetWindowRgn(Handle,regionHandle,true);