C# MySQL 不识别输入

Question

我正在使用本地 MySQL 数据库在 C# Visual Studio 中制作登录表单。但是，每次我输入信息时，它都会告诉我用户名和/或密码不正确，我知道这是错误的。 这是代码：

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 MySql.Data.MySqlClient;


namespace Dark_Heresy
{
    public partial class Form1 : Form
    {
        private MySqlConnection connection = new MySqlConnection();
        public Form1()
        {
            InitializeComponent();

        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void btn_Login_Click(object sender, EventArgs e)
        {
            try
            {
                String MyConnection = "datasource = localhost; port = 3306; username = root; password = Mypass;";
                MySqlConnection MyConn = new MySqlConnection(MyConnection);
                MySqlCommand SelectCommand = new MySqlCommand("SELECT * FROM dark_heresy.users WHERE users_='"+ this.TextUserName.Text + "' and password_='"+ this.TextPassword.Text + "';", MyConn);

                MySqlDataReader MyReader;
                MyConn.Open();
                MyReader = SelectCommand.ExecuteReader();
                int count = 0;
                while (MyReader.Read())
                {
                    count = count++;
                }
                if (count == 1)
                {
                    MessageBox.Show("Connection Successful");
                }
                else if (count > 1)
                {
                    MessageBox.Show("Duplication of Username and Password... Access Denied");
                }
                else

                    MessageBox.Show("Incorrect Username and/or Password");
                MyConn.Close();


            }
            catch (Exception exp)
            {
                MessageBox.Show("Error: \r\n" + exp);
            }


        }


        }
    }

在 MySQL 工作台中它可以工作，当进行此查询时，它会向我显示“用户”及其“密码”：

SELECT * FROM dark_heresy.users WHERE users_='admin' and password_='adminpass';

连接工作正常，已经过测试，但总是得到“用户名和/或密码不正确”的结果。

Answer 1

除了代码中的更多问题，您的问题是

count = count++;

后缀增量增加count，但返回其先前的值。

string connectionString = "datasource = localhost; port = 3306; username = root; password = Mypass;";
using(MySqlConnection myConn = new MySqlConnection(connectionString))
using(MySqlCommand selectCommand = new MySqlCommand())
{
    selectCommand.CommandText = "SELECT COUNT(1) FROM dark_heresy.users WHERE users_=@User and password_=@Password";
    selectCommand.Connection = myConn;
    selectCommand.Parameters.Add(new MySqlParameter("User", MySqlDbType.VarChar).Value = TextUserName.Text);
    selectCommand.Parameters.Add(new MySqlParameter("Password", MySqlDbType.VarChar).Value = TextPassword.Text);
    myConn.Open();
    var ret = selectCommand.ExecuteScalar();
    var count = Convert.ToInt32(ret);
    if (count == 1)
    {
         MessageBox.Show("Connection Successful");
    }
    else if (count > 1)
    {
         MessageBox.Show("Duplication of Username and Password... Access Denied");
    }
    else
    {
          MessageBox.Show("Incorrect Username and/or Password");
    }  
}