黑马程序员 C#学习笔记⑤ 省市县三级联动查询

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实现一个可以动态的进行省市县查询的程序

一 基本原理: 通过ADO.NET技术查询数据库, 并绑定到WPF控件中, 从而实现动态的省市县查询.

二 实现技术:

ADO.NET

数据绑定

三 实现步骤:

①首先进行数据库创建, 在网上下载一个省市县的数据库脚本. 部分内容如下图:



以上脚本创建了一个名叫AreaFull的表, 表中存储了个省市的信息.

AreaId----------表示该区域的Id

AreaName----表示该区域的名称

AreaPid--------表示该区域的直属上级区域

② 创建了数据库后, 在vs中使用ADO.NET技术来使用它.

先在App.Config中定义连接字符串

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
</startup>
<connectionStrings>
<add name="dbConn" connectionString="Data Source=.; Initial Catalog=MyTest; User ID=sa; Password=123456"/>
</connectionStrings>
</configuration>

定义完之后不能忘了添加引用System.Configuration

然后创建SqlHelper类, 在该类中定义对于数据库的操作

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 省市县联动查询
{
public static class SqlHelper
{
private static string connStr = ConfigurationManager.ConnectionStrings["dbConn"].ConnectionString;

public static DataTable ExecuteDataSet(string sql, params SqlParameter[] sqlParameters)
{
using (SqlConnection conn = new SqlConnection(connStr))
{
conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.Parameters.AddRange(sqlParameters);
cmd.CommandText = sql;
SqlDataAdapter adapter = new SqlDataAdapter(cmd);
DataSet dataSet = new DataSet();
adapter.Fill(dataSet);
return dataSet.Tables[0];
}
}
}

public static int ExecuteNonQuery(string sql, params SqlParameter[] sqlParameters)
{
using (SqlConnection conn = new SqlConnection(connStr))
{
conn.Open();
using (SqlCommand cmd = conn.CreateCommand())
{
cmd.Parameters.AddRange(sqlParameters);
cmd.CommandText = sql;
return cmd.ExecuteNonQuery();
}
}
}
}
}

③ 创建主程序

在主程序中需要使用Area类的对象来暂时存储查询信息, 定义如下:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace 省市县联动查询
{
public class Area
{
public int AreaID { get; set; }
public string AreaName { get; set; }
}
}

主窗口定义:

<Window x:Name="l" x:Class="省市县联动查询.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
Title="省市县联动查询" Height="350" Width="450" Loaded="l_Loaded">
<Grid>
<StackPanel Orientation="Horizontal">
<ListBox x:Name="ProvName" DisplayMemberPath="AreaName" Width="150" SelectionChanged="ProvName_SelectionChanged"></ListBox>
<ListBox x:Name="cityName" DisplayMemberPath="AreaName" Width="150" SelectionChanged="cityName_SelectionChanged"></ListBox>
<ListBox x:Name="countryName" DisplayMemberPath="AreaName" Width="150"></ListBox>
</StackPanel>
</Grid>
</Window>

给三个ListBox控件赋予Name属性用于后台调用, DisplayMemberPath用于绑定显示的值.

后台代码:

using System;
using System.Collections.Generic;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Data;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Imaging;
using System.Windows.Navigation;
using System.Windows.Shapes;

namespace 省市县联动查询
{
/// <summary>
/// MainWindow.xaml 的交互逻辑
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
}

private void l_Loaded(object sender, RoutedEventArgs e)
{
List<Area> listProv = new List<Area>();
//AreaPid 表示该区域直属的上级区域的 Id, Pid为0表示没有上级直属
DataTable table = SqlHelper.ExecuteDataSet("Select * from AreaFull where AreaPid=0");
//foreach (DataRow row in table.Rows)
//{
//    Area prov = new Area();
//    prov.AreaID = (int)row["AreaId"];
//    prov.AreaName = (string)row["AreaName"];
//    listProv.Add(prov);
//}
//定义一个方法多次使用, 代码复用
listProv = TableToList(table);
ProvName.ItemsSource = listProv;
}

private void ProvName_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
List<Area> listCity = new List<Area>();
Area prov = (Area)ProvName.SelectedItem;
int provId = prov.AreaID;
DataTable table = SqlHelper.ExecuteDataSet("Select * from AreaFull where AreaPid=@provId",
new SqlParameter("@provId", provId));
listCity = TableToList(table);
cityName.ItemsSource = listCity;
}

private void cityName_SelectionChanged(object sender, SelectionChangedEventArgs e)
{
List<Area> listCountry = new List<Area>();
Area city = (Area)cityName.SelectedItem;

//当第一级发生改动之后, 引起ProvName_SelectionChanged, 更改掉第二级的数据源
//这时会引发cityName_SelectionChanged, 并且由于当前的SelectedItem为null,
//所以如果不判断的话, 会引起异常.
if (city != null)
{
int cityId = city.AreaID;
DataTable table = SqlHelper.ExecuteDataSet("Select * from AreaFull where AreaPid=@cityId",
new SqlParameter("@cityId", cityId));
listCountry = TableToList(table);
countryName.ItemsSource = listCountry;
}
else
countryName.ItemsSource = null;
}

//将返回的表转换成List<Area>
private List<Area> TableToList(DataTable table)
{
List<Area> area = new List<Area>();
foreach (DataRow row in table.Rows)
{
Area city = new Area();
city.AreaID = (int)row["AreaId"];
city.AreaName = (string)row["AreaName"];
area.Add(city);
}
return area;
}
}
}

在后台中, 使用List<Area>类型的集合存储查找返回的信息, 然后将控件的ItemsSource绑定到该对象上.

注意:

在进行三级联动的时候, 需要对第三级进行SelectedItem的判断.

当第一级发生改动之后, 引起ProvName_SelectionChanged, 更改掉第二级的数据源
这时会引发cityName_SelectionChanged, 并且由于当前的SelectedItem为null,
所以如果不判断的话, 会引起异常

每个用于保存存储信息的集合都不能在外部声明, 除非使用ObserableList<>

效果图:



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ASP.Net+Unity开发、.Net培训、期待与您交流！ ----------------------详细请查看：www.itheima.com