在数据库中插入记录时，连接必须是有效且打开的

本文关键字：有效 连接 数据库 插入 记录 | 更新日期: 2023-09-27 18:05:43

我正在尝试将客户端详细信息插入数据库，但得到此异常

连接必须是有效且打开的。在MySql.Data.MySqlClient.MySqlCommand。Throw(Exception ex) at MySql.Data.MySqlClient.MySqlCommand. checkstate () at MySql.Data.MySqlClient.MySqlCommand. checkstate ()ExecuteReader(CommandBehavior行为)at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader() at MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery() at book_online。saveClient_Click(对象发送方，EventArgs e)

MySqlConnection con = new MySqlConnection();
con.ConnectionString = ConfigurationManager.ConnectionStrings("conio").ConnectionString();
MySqlCommand cmd = new MySqlCommand();
cmd.CommandText = "INSERT INTO clientsDetails (clientName, companyAddress, city, contactPersonName, contactNumber1) Values(@clientName, @companyAddress, @city, @contactPersonName, @contactNumber1)";
cmd.Parameters.AddWithValue("@clientName", companyName.Text);
cmd.Parameters.AddWithValue("@companyAddress", companyAddress.Text);
cmd.Parameters.AddWithValue("@city", companyCity.Text);
cmd.Parameters.AddWithValue("@contactPersonName", concernPersonName.Text);
cmd.Parameters.AddWithValue("@contactNumber1", countryCodeWithNumber);
con.Open();
cmd.ExecuteNonQuery();
con.Close();

在数据库中插入记录时，连接必须是有效且打开的

您已经打开了连接并执行了命令，但是您忘记了将连接分配给命令，那么只有代码才能像您预期的那样正常工作。强烈建议您也使用using。然后代码将如下所示:

using (MySqlConnection con = new MySqlConnection())
{
    con.ConnectionString = ConfigurationManager.ConnectionStrings("conio").ConnectionString();
    string queryText = "INSERT INTO clientsDetails (clientName, companyAddress, city, contactPersonName, contactNumber1) Values(@clientName, @companyAddress, @city, @contactPersonName, @contactNumber1)";
    using (MySqlCommand cmd = new MySqlCommand(queryText, con))
    {
        cmd.Parameters.AddWithValue("@clientName", companyName.Text);
        cmd.Parameters.AddWithValue("@companyAddress", companyAddress.Text);
        cmd.Parameters.AddWithValue("@city", companyCity.Text);
        cmd.Parameters.AddWithValue("@contactPersonName", concernPersonName.Text);
        cmd.Parameters.AddWithValue("@contactNumber1", countryCodeWithNumber);
        con.Open();
        cmd.ExecuteNonQuery();
    }
}

命令缺少connectionstring. 

MySqlConnection con = new MySqlConnection();
con.ConnectionString = ConfigurationManager.ConnectionStrings("conio").ConnectionString();
MySqlCommand cmd = new MySqlCommand();
cmd.Connection = con;
cmd.CommandText = "INSERT INTO clientsDetails (clientName, companyAddress, city, contactPersonName, contactNumber1) Values(@clientName, @companyAddress, @city, @contactPersonName, @contactNumber1)";
cmd.Parameters.AddWithValue("@clientName", companyName.Text);
cmd.Parameters.AddWithValue("@companyAddress", companyAddress.Text);
cmd.Parameters.AddWithValue("@city", companyCity.Text);
cmd.Parameters.AddWithValue("@contactPersonName", concernPersonName.Text);
cmd.Parameters.AddWithValue("@contactNumber1", countryCodeWithNumber);
con.Open();
cmd.ExecuteNonQuery();
con.Close();

您没有为您的命令指定连接对象:

cmd.Connection = con;

此外，最好使用using块，当它退出该块时自动关闭连接:

using(MySqlConnection con = new MySqlConnection())
{
   con.ConnectionString =
                       ConfigurationManager.ConnectionStrings("conio").ConnectionString();
   MySqlCommand cmd = new MySqlCommand();
   cmd.CommandText = @"INSERT INTO clientsDetails
              (clientName, companyAddress, city, contactPersonName, contactNumber1)
               Values
              (@clientName, @companyAddress, @city, @contactPersonName, @contactNumber1)";
   cmd.Connection = con;
   cmd.Parameters.AddWithValue("@clientName", companyName.Text);
   cmd.Parameters.AddWithValue("@companyAddress", companyAddress.Text);
   cmd.Parameters.AddWithValue("@city", companyCity.Text);
   cmd.Parameters.AddWithValue("@contactPersonName", concernPersonName.Text);
   cmd.Parameters.AddWithValue("@contactNumber1", countryCodeWithNumber);
   con.Open();
   cmd.ExecuteNonQuery();
}

仅供参考，using关键字让编译器为封闭的块生成try...finally，并在生成的finally块中的using(在您的情况下为con)内的对象上调用Dispose。所以在保证了finally的所有情况下连接都会被关闭

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