C#02WPF中无法使用ConfigurationManager的问题和一个省市选择类似的东西

源作者地址：https://blog.youkuaiyun.com/MOESE优快云/article/details/78107888

和form不一样，要自己引用程序集里面的System.configuration

using System;
using System.Collections.Generic;
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;
using System.Configuration;
using System.Data.SqlClient;

namespace _02SQLSelect {
    /// <summary>
    /// MainWindow.xaml 的交互逻辑
    /// </summary>
    public partial class MainWindow:Window {
        public MainWindow() {
            InitializeComponent();
        }

        private void Window_Loaded(object sender,RoutedEventArgs e) {
            //load data,
            string connStr = ConfigurationManager.ConnectionStrings["sqlConn"].ConnectionString;

            //crete link object
            using(SqlConnection conn = new SqlConnection(connStr)) {
                using(SqlCommand cmd = conn.CreateCommand()) {
                    conn.Open();
                    cmd.CommandText = @"select * from MyFirstDb.dbo.UserInfo";
                    using(SqlDataReader reader = cmd.ExecuteReader()) {
                        while(reader.Read()) {
                            
                            //AreaInfo areaInfo = new AreaInfo();
                           int AreadId = int.Parse(reader["UserId"].ToString());
                            //areaInfo.AreadName = (reader["UserAge"].ToString());
                            this.cbx.Items.Add(AreadId);

                        }

                    }
                }
            }
        //    this.cbx.SelectedIndex = 0;
        }

        private void cbx_SelectionChanged(object sender,SelectionChangedEventArgs e) {
           object area2 = this.cbx.SelectedItem;
            if(area2 == null) {
                return;
            }
            string connStr = ConfigurationManager.ConnectionStrings["sqlConn"].ConnectionString;

            //crete link object
            using(SqlConnection conn = new SqlConnection(connStr)) {
                using(SqlCommand cmd = conn.CreateCommand()) {
                    conn.Open();
                    cmd.CommandText = @"select * from MyFirstDb.dbo.UserInfo where UserId="+this.cbx.SelectedValue;
                    this.cbx_city.Items.Clear();
                    using(SqlDataReader reader = cmd.ExecuteReader()) {
                        while(reader.Read()) {

                            //AreaInfo areaInfo = new AreaInfo();
                            string UserAddress = reader["UserAddress"].ToString();
                            //areaInfo.AreadName = (reader["UserAge"].ToString());
                            this.cbx_city.Items.Add(UserAddress);

                        }

                    }
                }
            }
            this.cbx_city.SelectedIndex = 0;
        }
    }
}