相关疑难解决方法(0)

我是Visual Studio的新手.我正在创建一个登录表单.

我有这个代码.

string connectionString = ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString;
try
{
    using (OdbcConnection connect = new OdbcConnection(connectionString))
    {
        connect.Open();
        OdbcCommand cmd = new OdbcCommand("SELECT username, password FROM receptionist", connect);
        OdbcDataReader reader = cmd.ExecuteReader();

        if (username_login.Text == username && password_login.Text == password)
        {
            this.Hide();
            MessageBox.Show("Invalid User", "Login Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            this.Close();
        }
        else 
            MessageBox.Show("Invalid User", "Login Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        connect.Close();
    }
}
catch (OdbcException ex)
{
    MessageBox.Show(ex.Message, "error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}

但每当我尝试输入用户名和密码时,都会出现一个错误,称为配置系统无法初始化.我只是想知道这是什么问题,我怎么能解决这个问题？

请帮忙.

我使用log4net在C#中编写了一个测试控制台应用程序:

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

using log4net;
using log4net.Config;

[assembly: log4net.Config.XmlConfigurator(Watch = true)]

namespace Log4Net_Test
{
    class Program
    {
        private static readonly ILog log = LogManager.GetLogger(typeof(Program));

        static void Main(string[] args)
        {    
            log.Info("Entering application");    
            log.Debug("Debug message");    
            log.Info("Leaving application");
        }
    }
}

我的App.config文件看起来像这样:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <startup>
    <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
  </startup>
  <appSettings>
    <add key="log4net.Internal.Debug" value="true"/>
  </appSettings>
  <log4net>
    <!-- A1 is set to be a ConsoleAppender -->
    <appender name="A1" type="log4net.Appender.FileAppender"> …