通过下面代码在构造函数中调用方法 SetShadow();

即可实现无边框窗体的阴影效果了

需要添加命名空间 using System.Runtime.InteropServices;

复制代码 代码如下:
private const int CS_DropSHADOW = 0x20000;
private const int GCL_STYLE = (-26);

[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);

private void SetShadow()
{
SetClassLong(this.Handle, GCL_STYLE, GetClassLong(this.Handle, GCL_STYLE) | CS_DropSHADOW);
}