将文本框值与数据库进行比较

Question

So, I'm working on a project for a class of mine. The first part is a login form, which requires a user to enter a username and a password. When the login button is hit, the program is to compare the textbox text to what is in a datatable. Only problem is, I'm having a tough time doing this. I tried doing it with LINQ statements, but that made the values different from what I was expecting when I went to debug it. Am I doing something wrong here? Heres the code for the form.

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

namespace mcshonsey_Final
{
public partial class LoginForm : Form
{
    SortingClass sort = new SortingClass();

    mcshonsey_FinalProject.UserShowDBEntities dbcontext = null;

    public LoginForm()
    {
        InitializeComponent();
        textBox1.Text = "";
        textBox2.Text = "";
        textBox1.Focus();
    }

    private void button1_Click(object sender, EventArgs e)
    {
        if (dbcontext != null)
            dbcontext.Dispose();

        dbcontext = new mcshonsey_FinalProject.UserShowDBEntities();

            dbcontext.UserTables
                .OrderBy(entry => entry.UserID)
                .Load(); 

        if (string.IsNullOrEmpty(textBox1.Text) || string.IsNullOrEmpty(textBox2.Text))
        {
            MessageBox.Show("You must enter a password or username", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            textBox1.Focus();
        }

        /*else
        {
            ShowSelectForm ssf = new ShowSelectForm(this, sort);
            Hide();
            ssf.Show();
        }*/
        string num1 = Convert.ToString(textBox1.Text);
        string num2 = Convert.ToString(textBox2.Text);

        var user =
            from use in dbcontext.UserTables
            where use.UserName == num1
            select use;

        var user2 =
            from pas in dbcontext.UserTables
            where pas.UserPassword == num2
            select pas;

        if (textBox1.Text.Equals(user) && textBox2.Text.Equals(user2))
        {
            ShowSelectForm ssf = new ShowSelectForm(this, sort);
            Hide();
            ssf.Show();
        }

        else
        {
            MessageBox.Show("Incorrect username and/or password", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
            textBox1.Focus();
        }
    }

    private void button2_Click(object sender, EventArgs e)
    {
        if (MessageBox.Show("Are you sure you want to quit?", "Exit", MessageBoxButtons.YesNo) == DialogResult.Yes)
        {
            Application.Exit();
        }
    }

    private void LoginForm_Load(object sender, EventArgs e)
    {

    }
}
}

The SortingClass is a class to sort through the datatable, but that's for a later time. The UserShowDBEntities is the database itself.

Answer 1

I'm not a user of LINQ to SQL but I believe the following would work for you.

Basically, I made the following changes: 1. Combined the username and password check into a single WHERE clause 2. If you get a matching record back (ie Enumerable.Count check) it means the username and password matched a record and thus were correct.

private void button1_Click(object sender, EventArgs e)
{
    if (dbcontext != null)
        dbcontext.Dispose();

    dbcontext = new mcshonsey_FinalProject.UserShowDBEntities();

        dbcontext.UserTables
            .OrderBy(entry => entry.UserID)
            .Load(); 

    if (string.IsNullOrEmpty(textBox1.Text) || string.IsNullOrEmpty(textBox2.Text))
    {
        MessageBox.Show("You must enter a password or username", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        textBox1.Focus();
    }

    /*else
    {
        ShowSelectForm ssf = new ShowSelectForm(this, sort);
        Hide();
        ssf.Show();
    }*/

    var user =
        from use in dbcontext.UserTables
        where use.UserName == textBox1.Text && use.Password == textBox2.Text
        select use;

    if (Enumerable.Count(user) > 0)
    {
        ShowSelectForm ssf = new ShowSelectForm(this, sort);
        Hide();
        ssf.Show();
    }

    else
    {
        MessageBox.Show("Incorrect username and/or password", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        textBox1.Focus();
    }
}

Answer 2

I hope your data source is filled and your password is not encrypted in the database.

var user = dbcontext.UserTables.FirstOrDefault( u => u.UserName == textBox1.Text && u.UserPassword == textBox2.Text);

if(user != null)
   // Check
else
  // Failed

If textBox1 is the username and textBox2 is the password, this should work.