C#编写的windows计算器-源代码

C#编写的windows计算器-源代码(46)                     txtShow.Text="";
                    break;

            }
        }

        #endregion

        #region     主菜单事件
        //打开关于主题---调用windows XP中计算器的帮助
        private void menuItem5_Click(object sender, System.EventArgs e)
        {
            Help.ShowHelp(this,"C:\\WINDOWS\\Help\\calc.chm");       
        }

        //打开于我们
        private void menuItem6_Click(object sender, System.EventArgs e)
        {
            Form2 fm=new Form2();
            fm.Show();
           
        }

        //复制
        private void menuItem2_Click(object sender, System.EventArgs e)
        {
            if(txtShow.SelectionLength>0)
            {