C＃MySQL无法识别输入

Question

我使用C＃visual studio从本地MySQL数据库创建登录表单。然而，每次我输入信息时，都会告诉我用户名和/或密码不正确，我知道这是错误的。 这里是代码：

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工作台它的工作，它让我看到“用户”与它的“密码”时进行此查询：

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

的连接工作正常，它有已经过测试，但总是得到结果“不正确的用户名和/或密码”。

Answer 1

随着更多的问题在你的代码的问题是

count = count++; 

后缀增量递增count而是返回其先前的值。

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"); 
    } 
}