入門連接屬性尚未設置錯誤

正如標題所說，我試着寫一些事先準備好的聲明上的Visual Studio 2017年但是從我的程序的時候，我有一個例外，被稱爲入門連接屬性尚未設置錯誤

系統.InvalidOperationException：'連接屬性未設置爲 '。

下面是相關的代碼：

namespace Sequence 
{ 
    class Database 
    { 
    private MySqlCommand cmd; 
    MySql.Data.MySqlClient.MySqlConnection conn; //new connection 

    public void Connect() 
    { 
     string myConnectionString; //connection String 

     myConnectionString = "server=127.0.0.1;uid=root;" + 
    "pwd=;database=internship;"; 

     try 
     { 
      conn = new MySql.Data.MySqlClient.MySqlConnection(myConnectionString); 
      conn.Open(); 
     } 
     catch (MySql.Data.MySqlClient.MySqlException ex) 
     { 
      MessageBox.Show(ex.Message); 
     } 
    } 


    public void Disconnect() 
    { 
     try 
     { 
      conn.Close(); 
     } 
     catch (MySql.Data.MySqlClient.MySqlException ex) 
     { 
      MessageBox.Show(ex.Message); 
     } 
    } 

    public void AddData() 
    { 
     cmd = new MySql.Data.MySqlClient.MySqlCommand(); 
     //Connecting to database 
     Connect(); 
     try 
     { 
      //Prepare a statement 
      cmd.CommandText = "INSERT INTO storing VALUES(@longitude, @latitude, @status, @path)"; 
      cmd.Prepare(); 
      //Adding values 
      cmd.Parameters.AddWithValue("@longitude", 0.5); 
      cmd.Parameters.AddWithValue("@latitude", 0.5); 
      cmd.Parameters.AddWithValue("@status", "false"); 
      cmd.Parameters.AddWithValue("@path", "C:\\temp\\sequence"); 
      //Executes the Query 
      cmd.ExecuteNonQuery(); 
      //Writes in Console 
      Console.WriteLine("Line added successfully"); 
     } 
     catch (MySql.Data.MySqlClient.MySqlException ex) 
     { 
      MessageBox.Show("Error " + ex.Number + " has occured: " + ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Error); 
     } 



     } 

    } 
}

這是我的類，它連接到數據庫。我有一個主程序，我剛纔寫的：

static class Program 
{ 
    [STAThread] 
    static void Main() 
    { 
     Database db = new Database(); 
     db.Connect(); 
     db.AddData(); 
     db.Disconnect(); 
    } 
}

爲什麼我得到這個例外，任何想法？

我跟着這個鏈接教程： https://dev.mysql.com/doc/connector-net/en/connector-net-programming-prepared-preparing.html

在此先感謝

來源

2017-06-29 Stian Poisson