扩展RadioButton，实现在不同容器中互斥选择

扩展RadioButton，增加GroupName属性（默认为String.Empty)，如果GroupName相同，则不同容器中的RadioButton也可以互斥选择。代码如下：

public class RadioButtonEx : RadioButton
    {
        private string _groupName = string.Empty;

        public string GroupName
        {
            get { return _groupName; }
            set { _groupName = value; }
        }

        protected override void OnClick(EventArgs e)
        {
            UnCheckedRadioButton(this.TopLevelControl);
            this.Checked = true;
            base.OnClick(e);
        }

        private void UnCheckedRadioButton(Control parent)
        {
            if (parent != null && parent.Controls.Count > 0)
            {
                foreach (Control ctl in parent.Controls)
                {
                    UnCheckedRadioButton(ctl);
                    if (ctl is RadioButtonEx)
                    {
                        RadioButtonEx btn = (RadioButtonEx)ctl;
                        if (btn.GroupName.Equals(this.GroupName))
                        {
                            btn.Checked = false;
                        }
                    }
                }
            }
        }
    }