针对以上两个场景,我们可以用DropDownList直接绑定数据表,根据选择的省份动态加载该省份下的城市。光说不练,不是好汉,让我用一个小Demo来大家演示下详细过程吧。
Create Table Province
(
P
ROID int
Primary key,
ProN
ame v
Archar(20) not null
)
Create Table City
(
CityID int primary key,
ProID int for
eign key references Province(ProID),
CityName
VARchar(20)
)
Insert into Province values('1','北京')
Insert into Province values('2','河北')
Insert into Province values('3','山东')
insert into City values('1','1','海淀')
insert into City values('2','1','丰台')
insert into City values('3','1','大兴')
insert into City values('4','2','衡水')
insert into City values('5','2','廊坊')
insert into City values('6','2','保定')
insert into City values('7','3','济南')
insert into City values('8','3','烟台')
insert into City values('9','3','青岛')
p
ublic class DB
{
//连接数据库的字符串
public
static
SQLConnection CreateConnection()
{
SqlConnection con = new SqlConnection("Data Source=. ;Initial Cata
LOG=
test;uid=sa;pwd=123456;");
return con;
}
}
protected void Page_Load(object sender, Event
args e)
{
//如果窗体是第一次加载
if (!this.IsPostBack)
{
//绑定省份
SqlConnection con = DB.CreateConnection();
//打开数据库连接
con.O
PEn();
SqlCommand cmdProvince = new SqlCommand("select *
From Province", con);
SqlDataReader sdrProvince = cmdProvince.ExecuteReader();
//将sdrProvince中的内容绑定到ddlProvince下拉列表中
this.ddlProvince.DataSource = sdrProvince;
//需要显示的数据表Province中的内容
this.ddlProvince.DataTextField = "ProName";
//需要显示的数据表Province中的主键
this.ddlProvince.DataVal
UEFIeld = "ProID";
this.ddlProvince.DataBind();
sdrProvince.Close();
//关闭数据库连接
con.Close();
}
}
protected void ddlProvince_SelectedIndexChanged(object sender, EventArgs e)
{
SqlConnection con = DB.CreateConnection();
//打开数据库连接
con.Open();
//绑定城市
SqlCommand cmdCity = new SqlCommand("select * f
rom City where ProID=" + this.ddlProvince.SelectedValue, con);
SqlDataReader sdrCity = cmdCity.ExecuteReader();
//将sdrCity中的内容绑定到ddlCity下拉列表中
this.ddlCity.DataSource = sdrCity;
//需要显示的数据表City中的内容
this.ddlCity.DataTextField = "CityName";
//需要显示的数据表City中的主键
this.ddlCity.DataValueField = "CityID";
this.ddlCity.DataBind();
sdrCity.Close();
//关闭数据库连接
con.Close();
}
这样,我们就用DropDownList动态绑定数据表,实现了根据选择的省份动态下拉该省份下的城市的功能,达到了面向对象设计中解耦的目的,增强了代码的可维护性和用户的