c#之使用循环 c# 发送多封电子邮件时出现未指定错误_编程设计

我有一个用于管理业务的 Windows 窗体程序。我将所有客户的详细信息保存在数据库链接公司中。电子邮件地址。我有一个按钮，可以让我向邮件列表中的每个人发送一封电子邮件(下面的代码)。但是在发送了几封带有未指明错误的电子邮件后它崩溃了。我不知道为什么？我需要它从 CustomerID40- CustomerID1425 立即向所有客户发送相同的电子邮件。我们将不胜感激。抱歉，如果代码困惑。谢谢。错误:

System.Data.OleDb.OleDbException

HResult=0x80004005

Message=Unspecified error

Source=System.Data

StackTrace:

at System.Data.OleDb.OleDbConnectionInternal..ctor(OleDbConnectionString constr, OleDbConnection connection)

at System.Data.OleDb.OleDbConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningObject)

at System.Data.ProviderBase.DbConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)

at System.Data.ProviderBase.DbConnectionFactory.CreateNonPooledConnection(DbConnection owningConnection, DbConnectionPoolGroup poolGroup, DbConnectionOptions userOptions)

at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)

at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)

at System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)

at System.Data.ProviderBase.DbConnectionInternal.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory)

at System.Data.OleDb.OleDbConnection.Open()

at CourseworkDatabase.clsDBConnector.Connect() in C:\Users\rep\OneDrive\Desktop\Repairs\ Repairs_Database\CourseworkDatabase\CourseworkDatabase\clsDBConnector.cs:line 18

代码:

private void button6_Click_1(object sender, EventArgs e) 
{ 
    DialogResult dialogResult = MessageBox.Show("Are you sure to send email to all customers?(check code)", "Warning", MessageBoxButtons.YesNo); 
    if (dialogResult == DialogResult.Yes) 
    { 
        DoButtonTask(); 
    } 
} 
private void DoButtonTask() 
{ 
    for (int i = 40; i < 1425; i++) //40-1425 is customerID's 
    { 
        clsDBConnector dbConnector1 = new clsDBConnector(); 
        OleDbDataReader dr1; 
        string sqlStr1; 
        dbConnector1.Connect(); 
        sqlStr1 = " SELECT CustomerID, DateAdded, FullName, PhoneNumber, EmailAddress, SendOffersByEmail" + 
            " FROM Customer" +  
            " WHERE (CustomerID = " + i + ")"; 
        dr1 = dbConnector1.DoSQL(sqlStr1); 
        string name = ""; 
        string CustomerID = ""; 
        string email = ""; 
        string SendOffersBy_Email = ""; 
        DateTime date = DateTime.Now; 
        while (dr1.Read()) 
        {     
            CustomerID = CustomerID + Convert.ToString(dr1[0]); 
            name = name + dr1[2]; 
            email = email + Convert.ToString(dr1[4]); 
            SendOffersBy_Email = SendOffersBy_Email + Convert.ToString(dr1[5]); 
        } 
        if (email == "na" || email == "na@na.co.uk" || email == "na@na.com" || email == "") 
        { 
            //MessageBox.Show("Customer " + CustomerID + " does not have an email linked."); 
        } 
        else 
        { 
            if (SendOffersBy_Email == "yes" || SendOffersBy_Email == "Yes") 
            {     
                try 
                {     
                    SendEmail(i, email, name); 
                } 
                catch (Exception ex) 
                {     
                    MessageBox.Show(ex.ToString()); 
                } 
            } 
            else 
            {    
                //MessageBox.Show("Customer " + CustomerID + " does not accept emails."); 
            } 
        } 
    } 
    MessageBox.Show("Emails sent."); 
} 
 
private void SendEmail(int i, string email, string name) 
{     
    try 
    {     
        MailMessage mail = new MailMessage(); 
        SmtpClient SmtpServer = new SmtpClient("smtp.live.com"); 
        mail.From = new MailAddress("myemail"); 
        mail.To.Add(email); 
        mail.Subject = "PRICE DROP!! Have your iPhone repaired today."; 
        mail.Body = "Hi " + name + ",\n" +  
            "Our iPhone 7 and iPhone 8 series screen prices have now dropped in price!" +  
            " Reply to this email to have your iPhone booked in for repair today - the prices may go back up! " +  
            " All of our repairs come with our 6 months warranty and we can come to you." +  
            "\n\nKind regards,\n Your Mobile Phone & Tablet Repair Specialist." +  
            "\n\nTel: \nWebsite: \nEmail: " +  
            "\nFacebook: " +  
            "\n\n\n Don't want to recieve offers anymore? Just reply to this email to let us know and we will take you off our mailing system."; 
 
        SmtpServer.Port = 587; 
        SmtpServer.Credentials = new System.Net.NetworkCredential("myemail", "mypassword"); 
        SmtpServer.EnableSsl = true; 
        SmtpServer.Send(mail); 
        mail.Dispose(); 
    } 
    catch (Exception ex) 
    {     
        MessageBox.Show(ex.ToString()); 
    } 
}

请您参考如下方法:

代码有明显改进:

    for (int i = 40; i < 1425; i++) //40-1425 is customerID's 
    { 
        clsDBConnector dbConnector1 = new clsDBConnector(); 
        OleDbDataReader dr1; 
        string sqlStr1; 
        dbConnector1.Connect();  
        ... 
   }

此代码每次迭代都会打开您的数据库，这会增加开销，并且您的防病毒软件可能每次都在检查文件。

我建议将连接移到循环外(和关闭)，这样它就变成了

clsDBConnector dbConnector1 = new clsDBConnector(); 
OleDbDataReader dr1; 
string sqlStr1; 
dbConnector1.Connect(); 
for (int i = 40; i < 1425; i++) //40-1425 is customerID's 
{ 
   // process data 
} 
dbConnector1.Close();