C# 中 mysql 的问题

我在将c#与mysql数据库连接时遇到了一个小问题。当我尝试从文本框中插入值时，我收到以下错误。我想知道是否有人可以帮助我/向我解释我做错了什么。

这是我收到的错误："字段列表"中的未知列"测试"

这是我连接到数据库的代码：

namespace Planner
{
    internal class DBConnect
    {
        private MySqlConnection _connection = new MySqlConnection();
        private string _server;
        private string _database;
        private string _uid;
        private string _password;
        //private string _port;
        //private bool succes = false;

        //Constructor
        public DBConnect()
        {
            Initialize();
        }
        //Initialize values
        public void Initialize()
        {
            string connectionString2 = "Server=localhost;Port=3307;Database=test;Uid=root;Pwd=usbw";
            //+ "Port:" + _port + ";"
            _server = "localhost:3307";
            //_port = "3307";
            _database = "test";
            _uid = "root";
            _password = "usbw";
            string connectionString = "Server=" + _server + ";"  + "Database=" +
                               _database + ";" + "Uid=" + _uid + ";" + "Pwd=" + _password + ";";
            _connection = new MySqlConnection(connectionString2);
        }
        public bool OpenConnection()
        {
            try
            {
                _connection.Open();
                return true;
            }
            catch (MySqlException ex)
            {
                switch (ex.Number)
                {
                    case 0:
                        MessageBox.Show("Cannot connect to server");
                        break;
                    case 1042:
                        MessageBox.Show("Unable to connect to any of the specified MySQL hosts");
                        break;
                    case 1045:
                        MessageBox.Show("Invalid username/password");
                        break;
                }
                return false;
            }

        }
        private List<string>[] Select()
        {
            string selectquery = "SELECT * FROM tabelname";
            List<string>[] selectlist = new List<string>[3];
            selectlist[0] = new List<string>();
            selectlist[1] = new List<string>();
            selectlist[2] = new List<string>();

            MySqlCommand cmd = new MySqlCommand(selectquery, _connection);
            MySqlDataReader dataReader = cmd.ExecuteReader();

            while (dataReader.Read())
            {
                selectlist[0].Add(dataReader["waarde"] + "");
                selectlist[1].Add(dataReader["waarde"] + "");
                selectlist[2].Add(dataReader["waarde"] + "");
            }
            dataReader.Close();
            return selectlist;
        }
        public void Insert(string textvalue)
        {
            string insertquery = "INSERT INTO testconnectie(text) VALUES ("+textvalue+")";

                MySqlCommand cmd = new MySqlCommand(insertquery, _connection);
                cmd.ExecuteNonQuery();


        }
        private void Update()
        {
            string updatequery = "UPDATE tabelnaam SET waarde='', waarde'' WHERE waarde=''";
            MySqlCommand cmd = new MySqlCommand();
            cmd.CommandText = updatequery;
            cmd.Connection = _connection;
            cmd.ExecuteNonQuery();
        }
        private void Delete()
        {
            string deletequery = "DELETE FROM tabelnaam WHERE waarde=''";
            MySqlCommand cmd = new MySqlCommand(deletequery, _connection);
            cmd.ExecuteNonQuery();
        }
        public bool CloseConnection()
        {
            try
            {
                _connection.Close();
                return true;
            }
            catch (MySqlException ex)
            {
                MessageBox.Show(ex.Message);
                return false;
            }
        }

        public void Backup()
        {
            try
            {
                DateTime Time = DateTime.Now;
                int year = Time.Year;
                int month = Time.Month;
                int day = Time.Day;
                int hour = Time.Hour;
                int minute = Time.Minute;
                int second = Time.Second;
                int millisecond = Time.Millisecond;
                //Save file to C:' with the current date as a filename
                string path;
                path = "C:''ChatBackup" + year + "-" + month + "-" + day +
            "-" + hour + "-" + minute + "-" + second + "-" + millisecond + ".sql";
                StreamWriter file = new StreamWriter(path);

                ProcessStartInfo psi = new ProcessStartInfo();
                psi.FileName = "Database Backup";
                psi.RedirectStandardInput = false;
                psi.RedirectStandardOutput = true;
                psi.Arguments = string.Format(@"-u{0} -p{1} -h{2} {3}",
            _uid, _password, _server, _database);
                psi.UseShellExecute = false;
                Process process = Process.Start(psi);
                string output;
                output = process.StandardOutput.ReadToEnd();
                file.WriteLine(output);
                process.WaitForExit();
                file.Close();
                process.Close();
            }
            catch (IOException ex)
            {
                MessageBox.Show("Error , unable to backup! " + ex);
            }
        }

    }
}

麦因特

namespace Planner
{
    public partial class MainForm : Form
    {
        private DBConnect mysql = new DBConnect();

        public MainForm()
        {
            InitializeComponent();
            mysql.Initialize();
            mysql.OpenConnection();
        }
        private void _sendMessageButton_Click(object sender, System.EventArgs e)
        {
            string textvalue = _messageTextBox.Text;
            mysql.Insert(textvalue);
        }

        }
}

有人可以向我解释我做错了什么，提前谢谢。

string insertquery = "INSERT INTO testconnectie(text) VALUES ('"+textvalue+"')";

string insertquery = "INSERT INTO YourTableName ([yourColumnName]) VALUES (@ParameterName)";
using (var con = new MySqlConnection(connectionString))
using (var cmd = new MySqlCommand(insertquery, con))
{
    cmd.Parameters.AddWithValue("@ParameterName", textvalue); 
    con.Open();
    cmd.ExecuteNonQuery();
}