C# C MySQL查询不工作

错误消息是

连接必须有效且打开

这个代码错了吗？我怎样才能解决这个问题

string strConn = "server = localhost; user = root; database = ****; port = 3306; password = ****; Charset = utf8";
using (MySqlConnection conn = new MySqlConnection(strConn))
{
    MySqlCommand insertCommand = new MySqlCommand();

    conn.Open();

    for (int i = 0; i < 10; i++)
    {
        insertCommand.CommandText = "INSERT INTO master (col_name, col_code)" +
        " SELECT * from (select '" + _name[i] + "', '" + _code[i] + "') as tmp" +
        " WHERE NOT EXISTS (" +
        " SELECT col_code FROM master WHERE col_code = '" + _name[i] + "') limit 1;";

        insertCommand.ExecuteNonQuery();
    }
    conn.Close();
}

在for循环之前，需要为CommandObject设置连接，如：

InsertCommand.Connection = conn;

---

您需要使用您创建的conn连接对象将连接指定给您的命令

因此，您的代码如下所示：

string strConn = "server = localhost; user = root; database = ****; port = 3306; password = ****; Charset = utf8";
using (MySqlConnection conn = new MySqlConnection(strConn))
{
    MySqlCommand insertCommand = conn.CreateCommand();

    conn.Open();

    for (int i = 0; i < 10; i++)
    {
        insertCommand.CommandText = "INSERT INTO master (col_name, col_code)" +
        " SELECT * from (select '" + _name[i] + "', '" + _code[i] + "') as tmp" +
        " WHERE NOT EXISTS (" +
        " SELECT col_code FROM master WHERE col_code = '" + _name[i] + "') limit 1;";

        insertCommand.ExecuteNonQuery();
    }
    conn.Close();  //you don't need this.
}

---

你指向的代码在哪里？你能在这里插入你的代码吗？我添加了图像，但无法加载。什么是无法加载？不要发布图像，而是发布你的代码。使用MySqlconnection conn=new MysqlConnectionstrconnIt wors！谢谢：@lovendon如果它有效，那么适当的回答将是投票并将其标记为已回答：

string strConn = "server = localhost; user = root; database = ****; port = 3306; password = ****; Charset = utf8";
using (MySqlConnection conn = new MySqlConnection(strConn))
{
    MySqlCommand insertCommand = conn.CreateCommand();

    conn.Open();

    for (int i = 0; i < 10; i++)
    {
        insertCommand.CommandText = "INSERT INTO master (col_name, col_code)" +
        " SELECT * from (select '" + _name[i] + "', '" + _code[i] + "') as tmp" +
        " WHERE NOT EXISTS (" +
        " SELECT col_code FROM master WHERE col_code = '" + _name[i] + "') limit 1;";

        insertCommand.ExecuteNonQuery();
    }
    conn.Close();  //you don't need this.
}

using (MySqlConnection conn = new MySqlConnection(strConn))
{
    //your code
}