如何将数据从数据库传输到文本框？

问题描述：

我不能将数据从数据库传输到文本框。请帮帮我。

I can not do transferring data to textboxes from database. Help me please.

="c#">using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using MySql.Data.MySqlClient;

namespace WindowsFormsApplication1
{
    public partial class Form4 : Form
    {
        public Form1 frm1;
        public Form2 frm2;
        public Form3 frm3;
        public Form4 frm4;
        public Form4()
        {
            InitializeComponent();
        }

        private void Form4_Load(object sender, EventArgs e)
        {
            try
            {
                int a = 0;

            string wanted, id, username, password, email, secureword, name, surname, age, gender, country;
            MySqlConnection conn = new MySqlConnection("server=localhost;database=naperva;user=root;password=");
            MySqlCommand cmd = new MySqlCommand("SELECT * FROM users WHERE id, username, password, email, secureword, name, surname, age, gender, country", conn);
            MySqlDataReader read = null;
            conn.Open();
            read = cmd.ExecuteReader();
            wanted = frm1.loginUsername_txt.Text;

            while (read.Read())
            {
                id = read["id"].ToString();
                username = read["username"].ToString();
                password = read["password"].ToString();
                email = read["email"].ToString();
                secureword = read["secureword"].ToString();
                name = read["name"].ToString();
                surname = read["surname"].ToString();
                age = read["age"].ToString();
                gender = read["gender"].ToString();
                country = read["country"].ToString();

                if (wanted == username)
                {
                    id = myprofileID_txt.Text;
                    username = myprofileUsername_txt.Text;
                    password = myprofilePassword_txt.Text;
                    email = myprofileEmail_txt.Text;
                    secureword = myprofileSecureWord_Txt.Text;
                    name = myprofileName_txt.Text;
                    surname = myprofileSurname_txt.Text;
                    gender = myprofileGender_comboBox.Text;
                    age = myprofileAge_txt.Text;
                    country = myprofileCountry_txt.Text;
                    a = 1;
                }

                if (a != 1)
                {
                    MessageBox.Show("Not found");
                    read.Close();
                    conn.Close();
                }
            }
            }
            catch (Exception)
            {
                MessageBox.Show("DATABASE ERROR");
            }
        }
    }
}

答

你几乎拥有它。这个代码是你从某个地方复制的吗？

要放入文本框，你可以：

You almost have it. Is this code you copied from somewhere?

To put in textboxes you do:

myprofileCountry_txt.Text = country;

我写了这段代码。我收到了错误行：

I wrote this codes. I received the error line:

read = cmd.ExecuteReader();

共有4种表格。全部互连。

There are a total of 4 forms. All interconnected.

public Form1()
        {
            InitializeComponent();

            frm2 = new Form2();
            frm3 = new Form3();
            frm4 = new Form4();
            frm2.frm1 = this;
            frm3.frm1 = this;
            frm4.frm1 = this;

        }

我用各种形式写的相同：

I wrote the same in all forms:

public Form1 frm1;
        public Form2 frm2;
        public Form3 frm3;
        public Form4 frm4;

有报名表和将成员添加到数据库表单。单击一个按钮打开Form4（我的个人资料）。在Form4中，在写入数据时注册。对不起，发给我不明白的代码。抱歉我的英语：）

There are entry form and add members to the database form. When the click a button open the Form4(My Profile). In the Form4, sign up, while writing data. Sorry, send you the code I did not understand. And sorry for my English :)

问题与您的sql语句有关，更改

issue is with your sql statement, change

MySqlCommand cmd = new MySqlCommand("SELECT * FROM users WHERE id, username, password, email, secureword, name, surname, age, gender, country", conn);

wanted = frm1.loginUsername_txt.Text;
MySqlCommand cmd = new MySqlCommand("SELECT * FROM users WHERE username ='"+wanted +"'", conn);

你最好检查一下sql的语法 [ ^ ]并且还将字符串与sql语句连接不安全，它将打开sql注入atacks。我会使用参数，如果它只是用于验证用户是否存在;示例代码：

you better check the sql where syntax [^] and also concatenating strings not safe way with sql statements, it will open sql injection atacks. I would use parameters and if it it is only for validating user exist or not; sample code:

public bool ValidateUser(string username, string password)
{
    int count = 0;
    string query = "SELECT count(*) FROM users WHERE username = @user AND password = @pass";
    using(MySqlConnection conn = new MySqlConnection("server=localhost;database=naperva;user=root;password="))
    using (MySqlCommand cmd = new MySqlCommand(query, conn))
    {
        cmd.Parameters.Add(new MySqlParameter("@user", username));
        cmd.Parameters.Add(new MySqlParameter("@pass ", password));

        connector.Open();
        count = int.Parse(cmd.ExecuteScalar().ToString());
    }

    return count > 0;
}

如何将数据从数据库传输到文本框？

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