第20课-数据库开发及ado.net 可空值类型,资料管理器,多条件查询,Case

第20课-数据库开发及ado.net

可空值类型,资料管理器,多条件查询,Case

SqlHelper

using System;

using System.Collections.Generic;

using System.Configuration;

using System.Data;

using System.Data.SqlClient;

using System.Text;

namespace _02省市联动

{

public static  class SqlHelper

{

//常量 无法修改

private const string A = "aaa";

//readonly 是一个只读的变量,只能在声明或构造函数中修改

//只读变量只能在构造函数或者是一开始声明变量的时候赋值，不允许在其它地方为变量赋值。

//连接字符串

private static readonly string conStr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;

/// <summary>

/// 封装一个ExecuteNonQuery方法,执行insert、delete、updata

/// </summary>

/// <param name="sql"></param>

/// <param name="pms"></param>

/// <returns></returns>

public static int ExecuteQuery(string sql,params SqlParameter[] pms)

{

using (SqlConnection con=new SqlConnection (conStr))

{

using (SqlCommand com=new SqlCommand (sql,con))

{

if (pms!=null)

{

com.Parameters.AddRange(pms);

}

con.Open();

return com.ExecuteNonQuery();

}

}

}

/// <summary>

/// 封装返回一个单个值的方法

/// </summary>

/// <returns></returns>

public static object ExecuteScalar(string sql,params SqlParameter[] pms)

{

using (SqlConnection con = new SqlConnection(conStr))

{

using (SqlCommand com=new SqlCommand (sql,con))

{

if (pms!=null)

{

com.Parameters.AddRange(pms);

}

con.Open();

return com.ExecuteScalar();

}

}

}

/// <summary>

/// 封装一个返回SqlDataReader的方法

/// </summary>

/// <returns></returns>

public static SqlDataReader  ExecuteReader(string sql,params SqlParameter[] pms)

{

SqlConnection con=new SqlConnection (conStr);

using (SqlCommand com=new SqlCommand (sql,con))

{

if (pms!=null)

{

com.Parameters.AddRange(pms);

}

try

{

con.Open();

return com.ExecuteReader(System.Data.CommandBehavior.CloseConnection);

}

catch (Exception)

{

con.Close();

con.Dispose();

throw;

}

}

}

public static DataTable ExecuteDataTable(string sql,params SqlParameter[] pms)

{

DataTable dt = new DataTable();

using (SqlDataAdapter adapter=new SqlDataAdapter (sql,conStr ))

{

//如何添加参数

adapter.Fill(dt);

}

return dt;

}

}

}

省市联动

using System;

using System.Collections.Generic;

using System.Text;

namespace _02省市联动

{

public  class ProvinceItem

{

public int AreaId {get ;set;}

public string AreaName{get ;set;}

public int AreaPid{get ;set;}

public override string ToString()

{

return this.AreaName;

}

}

}

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Data.SqlClient;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

namespace _02省市联动

{

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

private void Form1_Load(object sender, EventArgs e)

{

//加载省份信息到第一个ComboBox

LoadProvince();

//设置俩个下拉菜单的默认值为“请选择”

comboBox1.SelectedIndex = 0;

comboBox2.SelectedIndex = 0;

}

private void LoadProvince()

{

string sql = "select * from TblArea where AreaPId  =0";

using (SqlDataReader reader=SqlHelper .ExecuteReader(sql))

{

{

if (reader .HasRows)

while(reader .Read())

{

ProvinceItem item = new ProvinceItem();

item.AreaId = reader.GetInt32(0);

item.AreaName = reader.GetString(1);

item.AreaPid = reader.GetInt32(2);

comboBox1.Items.Add(item);

}

}

}

//为ComboBox 增加一个“请选择”

ProvinceItem itemDefault = new ProvinceItem();

itemDefault.AreaId = -1;

itemDefault.AreaName = "请选择";

comboBox1.Items.Insert(0, itemDefault);

}

/// <summary>

/// 下拉菜单的选择项改变事件

/// </summary>

/// <param name="sender"></param>

/// <param name="e"></param>

private void comboBox1_SelectedValueChanged(object sender, EventArgs e)

{

//获取当前用户选择的项

if (comboBox1.SelectedIndex > 0)

{

//加载第二个下来菜单，数据来源：根据第一个下拉菜单用户选项的AeraId来查询该项的所有子项

//获取当前选中项的ID

ProvinceItem item=comboBox1.SelectedItem as ProvinceItem;

int areaId = item.AreaId;

LoadCity(areaId);

}

}

private void LoadCity(int areaId)

{

comboBox2.Items.Clear();

string sql = "select * from TblArea where AreaPId=@aid";

using (SqlDataReader reader = SqlHelper.ExecuteReader(sql, new SqlParameter("@aid", areaId)))

{

if (reader .HasRows )

{

while (reader.Read())

{

ProvinceItem item = new ProvinceItem();

item.AreaId = reader.GetInt32(0);

item.AreaName = reader.GetString(1);

item.AreaPid = reader.GetInt32(2);

comboBox2.Items.Add(item);

}

}

}

//也添加一个“请选择”

ProvinceItem itemDefault = new ProvinceItem();

itemDefault.AreaId = -1;

itemDefault.AreaName = "请选择";

comboBox2.Items.Insert(0, itemDefault);

comboBox2.SelectedIndex = 0;

}

}

}

省市数据递归加载到TreeView

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Data.SqlClient;

using System.Drawing;

using System.Text;

using System.Windows.Forms;

namespace _03省市数据递归加载到TreeView

{

public partial class Form1 : Form

{

public Form1()

{

InitializeComponent();

}

private void button1_Click(object sender, EventArgs e)

{

////1.把所有的省份及直辖市加载到TreeView的根节点上

//List<Area> listProvince = GetSubItemByParentId(0);

//foreach (Area  item in listProvince)

//{

//    treeView1.Nodes.Add(item .AreaName );

//}

//递归将省市加载到TreeView中

LoadDataToTree(treeView1.Nodes,0);

}

private void LoadDataToTree(TreeNodeCollection treeNodeCollection, int pid)

{

//1.根据指定的Pid获取该城市下的子城市

List<Area> listCity = GetSubItemByParentId(pid);

//2.遍历将获取到的数据绑定到TreeNodeCollection节点集合中

foreach (var item in listCity )

{

//返回刚刚添加的这个节点

TreeNode node = treeNodeCollection.Add(item.AreaName);

LoadDataToTree(node.Nodes ,item.Areaid);

}

}

//封装一个方法，根据父ID查询下面的所有子项

private List<Area> GetSubItemByParentId(int pid)

{

List<Area> list = new List<Area>();

string sql = "select * from TblArea where areaPid=@pid";

using (SqlDataReader reader = SqlHelper .ExecuteReader (sql,new SqlParameter ("@pid",pid)))

{

if (reader .HasRows )

{

while (reader .Read ())

{

Area model = new Area();

model.Areaid = reader.GetInt32(0);

model.AreaName = reader.GetString(1);

model.AreaPid = reader.GetInt32(2);

list.Add(model);

}

}

}

return list;

}

}

}

using System;

using System.Collections.Generic;

using System.Text;

namespace _03省市数据递归加载到TreeView

{

public  class Area

{

public int Areaid { get; set; }

public string AreaName { get; set; }

public int AreaPid { get; set; }

}

}