登陆

-----------------------------配置文件---------------------------------------------------------------------------------------------

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup>
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
    </startup>
  <connectionStrings>
    <add name="sql" connectionString="server=.;database=MySecondDB;uid=sa;pwd=520;"/>
  </connectionStrings>
</configuration>

----------------------------Program.cs------------------------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace _08登陆
{
    static class Program
    {
        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }
    }
}

-----------------------------Form1-------------------------------------------------------------------------------------------------

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace _08登陆
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void btnLogin_Click(object sender, EventArgs e)
        {
            // 如何表示登陆成功了

            string uid = txtUid.Text.Trim();
            string pwd = txtPwd.Text;

            // 验证
            string connStr = ConfigurationManager.ConnectionStrings["sql"].ConnectionString;

            string sql = "select count(*) from loginPrimaryTest where uid= '" + uid + "' and pwd='" + pwd + "'";
            int count;
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                // 执行对象
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    conn.Open();
                    count = (int)cmd.ExecuteScalar();
                }
            }
            if (count > 0)
            {
                MessageBox.Show("登陆成功");
            }
            else
            {
                MessageBox.Show("用户名或密码错误");
            }
        }
    }
}

遇到的问题： 发现添加 using System.Configuration 后 ConfigurationManager 依然无效

解决的方法： 在项目的 Reference 中 添加 System.Configuraton