从 Mysql 中搜索数据并将其设置到文本框 c#答案

【问题标题】：Search Data From Mysql and Set it into Textbox c#从 Mysql 中搜索数据并将其设置到文本框 c#
【发布时间】：2022-01-11 22:35:55
【问题描述】：

我正在尝试制作一个程序，从 MySQL 数据库中搜索数据并使用 Text Change 事件在文本框中显示值。

到目前为止，这是我的代码：

private void textBox1_TextChanged(object sender, EventArgs e)
{       
    string sqlstring = "database = db_phonebook; user = root; password = ''; server = 'localhost'; SSL Mode = None";
    MySqlConnection mysqlcon = new MySqlConnection(sqlstring);
    MySqlCommand mysqlcom;
    MySqlDataReader mdr;
    
    mysqlcon.Open();
    
    string selectquery = "SELECT * FROM 'tbl_phonebook' WHERE CID =" + cid.Text;
    mysqlcom = new MySqlCommand(selectquery, mysqlcon);
    
    mdr = mysqlcom.ExecuteReader();
    
    if (mdr.Read())
    {
        name.Text = mdr.GetString("Name");
        address.Text = mdr.GetString("Address");
        contact.Text = mdr.GetString("Contact_Number");
        email.Text = mdr.GetString("Email_Address");
    }
    else
    {
        MessageBox.Show("Record Not Found!");
    }
    
    mysqlcon.Close();        
}

但是错误提示 MySql.Data.MySqlClient.MySqlException: 'You have an error in your SQL syntax;查看与您的 MariaDB 服务器版本相对应的手册，了解在第 1 行的“tbl_phonebook”WHERE CID =' 附近使用的正确语法

知道如何解决这个问题吗？

【问题讨论】：

您想要反引号（tab 键上方的键）而不是单引号。您也真的不想直接将任意文本框输入直接发送到数据库。对于只有一点知识的人来说，使用它来执行诸如删除数据库中的所有表之类的事情是微不足道的。
这样查询 "SELECT * FROM 'tbl_phonebook' WHERE CID ="'+cid.Text+'";
@SANDEEP Noooo，这在至少两种不同的方面仍然是错误的，可能是三种。

标签： c# mysql database

【解决方案1】：

很抱歉，这里有很多错误，其中一些甚至比您所知道的错误更重要。试试这个，并从显示的模式中学习：

private void textBox1_TextChanged(object sender, EventArgs e)
{       
    string constring = "database = db_phonebook; user = root; password = ''; server = 'localhost'; SSL Mode = None";
    //backticks instead of single quotes around the table/object name
    string sql = "SELECT * FROM `tbl_phonebook` WHERE CID = @CID";
    //using blocks make sure the connection is closed and disposed, 
    // EVEN IF AN EXCEPTION IS THROWN
    // Original code would have left the connection hanging open.
    using (var con = new MySqlConnection(constring))
    using(var cmd = new MySqlCommand(sql, con))
    {
        //parameterized query instead of string concatenation.
        // THIS IS A **HUGE** DEAL!!
        // It's important enough you should STOP and go FIX
        // any code you have anywhere that already uses concatenation.
        cmd.Parameters.AddWithValue("@CID", cid.Text);
        con.Open();
        using (var mdr = cmd.ExecuteReader())
        {
    
            if (mdr.Read())
            {
                name.Text = mdr.GetString("Name");
                address.Text = mdr.GetString("Address");
                contact.Text = mdr.GetString("Contact_Number");
                email.Text = mdr.GetString("Email_Address");
            }
            else
            {
                //Do NOT show an interrupting textbox that steals focus from
                // an actively typing user based on a textchanged event!

                name.Text = "";
                address.Text = "";
                contact.Text = "";
                email.Text = "";
            }
        }
    }      
}

【讨论】：