给listview赋值的方法：
peopledata peo = new peopledata();
List<people> pl = peo.selectall();
foreach (people x in pl)
{
ListViewItem l = new ListViewItem();
l.Text = x.ids.ToString();
l.SubItems.Add(x.name);
l.SubItems.Add(x.pwd );
l.SubItems.Add(x.nickname);
l.SubItems.Add(x.sexstr);
l.SubItems.Add(x.birthdaystr);
l.SubItems.Add(x.nationname);
listView1.Items.Add(l);
}
------------------------
Application.Exit(); --关闭所有form;
form2 f =new form2();
f.show(); ---打开form2;
--
f.showDialog(); ---form2不关闭，父页面无法操作;
--
f.owner=this; ---form2始终仅遮盖父页面;
--
public list<form> fl =new list<form>;
form2 f=new form2(this);
bool b= false;
form1.bottom.click()
{
foreach(form2 x in fl){
if(x is form2){
}
else{
b=true;
}
}
}
if(b){
f.show();
fl.add(f);
}
form1 f1;
public form2 (form1 f)
{
f1=f;
}
public form closeing(){
f1.fl.remove(this);
} ----唯一页面;
------------------------------
Button b2 = sender as Button; 所有按钮都可以选中该事件；
chinastates c = comboBox1.SelectedItem as chinastates; 将combobox1中选中项作为类中的一条属性，从而找出类中的其他属性；