用户控件回发事件到主窗口的方法

public partial class TestUC : UserControl
{
    public event UCHandler UCEvent;

    private void btnTest_Click(object sender, EventArgs e)
        {
             UCEvent arg = new UCEvent();
             arg.str = "12345";
             this.UCEvent(this, arg);
        }
} 
主窗口加入代码

private void Event(object sender, UCEvent e)
{
    label1.Text=e.str;
}

private void frmMainWindow_Load(object sender, EventArgs e)
{
    TestUC uc=new TestUC();
    uc.UCEvent += new UCHandler(Event);
    panelMain.Controls.Add(uc);
}