在窗体form代码中加入如下代码即可：
protected override CreateParams CreateParams
{ get
{ CreateParams cp = base.CreateParams; cp.ExStyle |= 0x02000000; return cp; } }
UserControl的Code
protected override CreateParams CreateParams {
get {
var parms = base.CreateParams;
parms.Style &= ~0x02000000; // Turn off WS_CLIPCHILDREN
return parms;
}
}