如何编码登录表单 [英] How to Code Log-in form

问题描述

Hello Everyone

我正在为我的学校项目创建一个程序

现在我在我的程序的登录表单中工作。



我收到异常错误对象引用没有设置为对象的实例

at

 ConfigurationManager.ConnectionStrings [  ConnData]。ConnectionString; 

 使用系统; 
 使用 System.Windows.Forms; 
 使用 System.Collections.Generic; 
 使用 System.ComponentModel; 
 使用 System.Net; 
 使用 System.Data.Sql; 
 使用 System.Configuration; 
 使用 System.Collections.Specialized; 
 使用 System.Linq; 
 使用 System.Text; 
 使用 System.Windows; 
 使用 System.Windows.Controls; 
 使用 System.Windows.Data; 
 使用 System.Windows.Documents; 
 使用 System.Windows.Input; 
 使用 System.Windows.Media; 
 使用 System.Windows.Media.Imaging; 
 使用 System.Windows.Navigation; 
 使用 System.Windows.Shapes; 
 使用 System.Data; 
 使用 System.Data.SqlClient; 
 使用 System.Text.RegularExpressions; 
 使用 System.Runtime.InteropServices; 
 
 
 命名空间 Proj.Data 
 {
  / //   <  摘要 >  
   ///  交互逻辑for MainWindow.xaml 
   ///   < ;   / summary  >  
   public   partial   class 登录：Window 
 {
  public 登录（）
 {
 InitializeComponent（）; 
  new  SplashWindow（）。ShowDialog（）; 
 
} 
 私有  void  Window_Loaded（ object  sender，RoutedEventArgs e）
 {
 
} 
 
 
  private   void  Exit_Click（ object  sender，RoutedEventArgs e）
 {
  this  .Close（）; 
} 
 
 
 私人  void  Button1_Click（< span class =code-keyword> object  sender，RoutedEventArgs e）
 {
  if （（textBox1.Text！=  ）&&（passwordbox1.Password！=  ））
 {
  string  connstring = ConfigurationManager .ConnectionStrings [  ConnData]。ConnectionString; 
 SqlConnection con =  new  SqlConnection（connstring）; 
  string  q =   select * from Login UserId = @Username和Password = @Password; 
 SqlCommand cmd =  new  SqlCommand（q，con）; 
 cmd.Parameters.AddWithValue（  @ Username，此 .textBox1.Text）; 
 cmd.Parameters.AddWithValue（  @ Password，此 .passwordbox1.Password）; 
 con.Open（）; 
 SqlDataReader dr = cmd.ExecuteReader（）; 
  while （dr.Read（））
 {
  if  （dr.HasRows ==  true ）
 {
 System.Windows.MessageBox.Show（  登录成功完成）; 
} 
} 
 如果（dr.HasRows ==  false  ）
 {
 textBlock5.Visibility = System.Windows.Visibility.Visible; 
} 
  else  
 {
 textBlock5.Visibility = System.Windows.Visibility.Visible; 
} 
} 
} 
 
  private   void  textBox1_TextChanged（ object  sender，TextChangedEventArgs e）
 {
 textBlock5.Visibility = System.Windows.Visibility.Hidden; 
  if （Keyboard.GetKeyStates（Key.CapsLock）== KeyStates.Toggled）
 {
 textBlock4.Visibility = System.Windows .Visibility.Visible; 
} 
  else  
 {
 textBlock4.Visibility = System.Windows.Visibility.Hidden; 
} 
} 
 
  private   void  passwordbox1_PasswordChanged（  object  sender，RoutedEventArgs e）
 {
 textBlock5.Visibility = System.Windows.Visibility.Hidden; 
  if （Keyboard.GetKeyStates（Key.CapsLock）== KeyStates.Toggled）
 {
 textBlock4.Visibility = System.Windows .Visibility.Visible; 
} 
  else  
 {
 textBlock4.Visibility = System.Windows.Visibility.Hidden; 
} 
 
} 
 
 
 
 
} 
} 

我对C＃和Sql有一点了解，总是在寻找Google for Tutorial，它让我感到困惑。



或请你为我的登录建议一个新的代码

解决方案

这些可能对你有帮助 -

视频1 [ ^ ]

视频2 [ ^ ]

Hello Everyone
I'm Creating a Program, for my School project
now I am working at Login form of my Program.

I am getting Exception Error "Object reference not set to an instance of an object"
at

ConfigurationManager.ConnectionStrings["ConnData"].ConnectionString;

using System;
using System.Windows.Forms;
using System.Collections.Generic;
using System.ComponentModel;
using System.Net;
using System.Data.Sql;
using System.Configuration;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
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.Data;
using System.Data.SqlClient;
using System.Text.RegularExpressions;
using System.Runtime.InteropServices;


namespace Proj.Data
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class Login : Window
    {
        public Login()
        {
            InitializeComponent();
            new SplashWindow().ShowDialog();
            
        }
       private void Window_Loaded(object sender, RoutedEventArgs e)
        {
           
        }

        
        private void Exit_Click(object sender, RoutedEventArgs e)
        {
            this.Close();
        }


        private void Button1_Click(object sender, RoutedEventArgs e)
        {
            if ((textBox1.Text != "") && (passwordbox1.Password != ""))
            {
                string connstring = ConfigurationManager.ConnectionStrings["ConnData"].ConnectionString;
                SqlConnection con = new SqlConnection(connstring);
                string q = "select * from Login where UserId = @Username and Password = @Password ";
                SqlCommand cmd = new SqlCommand(q, con);
                cmd.Parameters.AddWithValue("@Username", this.textBox1.Text);
                cmd.Parameters.AddWithValue("@Password", this.passwordbox1.Password);
                con.Open();
                SqlDataReader dr = cmd.ExecuteReader();
                while (dr.Read())
                {
                    if (dr.HasRows == true)
                    {
                        System.Windows.MessageBox.Show("Login Successfully Done");
                    }
                }
                if (dr.HasRows == false)
                {
                    textBlock5.Visibility = System.Windows.Visibility.Visible;
                }
                else
                {
                    textBlock5.Visibility = System.Windows.Visibility.Visible;
                }
            }
        }
       
        private void textBox1_TextChanged(object sender, TextChangedEventArgs e)
        {
            textBlock5.Visibility = System.Windows.Visibility.Hidden;
            if (Keyboard.GetKeyStates(Key.CapsLock) == KeyStates.Toggled)
            {
                textBlock4.Visibility = System.Windows.Visibility.Visible;
            }
            else
            {
                textBlock4.Visibility = System.Windows.Visibility.Hidden;
            }
        }

        private void passwordbox1_PasswordChanged(object sender, RoutedEventArgs e)
        {
            textBlock5.Visibility = System.Windows.Visibility.Hidden;
            if (Keyboard.GetKeyStates(Key.CapsLock) == KeyStates.Toggled)
            {
                textBlock4.Visibility = System.Windows.Visibility.Visible;
            }
            else
            {
                textBlock4.Visibility = System.Windows.Visibility.Hidden;
            }
            
        }

       

       
    }
}

I have a little knowledge about C# and Sql, always looking for Google for Tutorial and it keeps me puzzled.

or Please you can suggest a new Code for my Login

解决方案

These might help you -
Video 1[^]
Video 2[^]

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