C# 无法访问该文件，因为它已被其他进程使用

Question

我有将 SQL 转换为 CSV 的代码:

public void CreateCSVFile(DataTable dt, string strFilePath, bool Is_Ordre, int TypeDonne)
{

    //FileStream fs = new FileStream(strFilePath, FileMode.Create);
    // FileStream fs = File.Create(strFilePath);

    // Create the CSV file to which grid data will be exported.
    //StreamWriter sw = new StreamWriter(fs);
    //StreamWriter sw = new StreamWriter(strFilePath, false);
    using (var sw = new StreamWriter(strFilePath, false))
    {
        // First we will write the headers.
        //DataTable dt = m_dsProducts.Tables[0];
        int iColCount = dt.Columns.Count;
        for (int i = 0; i < iColCount; i++)
        {
            sw.Write(dt.Columns[i]);
            if (i < iColCount - 1)
            {
                sw.Write(",");
            }
        }
        if (Is_Ordre) sw.Write(", TYP_DONNE");

        sw.Write(sw.NewLine);

        // Now write all the rows.
        foreach (DataRow dr in dt.Rows)
        {
            for (int i = 0; i < iColCount; i++)
            {
                if (!Convert.IsDBNull(dr[i]))
                {
                    sw.Write("\'" + dr[i].ToString().Replace("'", " ").Replace(",", ".") + "\'");
                }
                else
                {
                    sw.Write("\' \'");
                }
                if (i < iColCount - 1)
                {
                    sw.Write(",");
                }
            }
            if (Is_Ordre) sw.Write(", \'" + TypeDonne + "\'");
            sw.Write(sw.NewLine);
        }                
        sw.Flush();
        sw.Close();
        sw.Dispose();
    }
        //fs.Close();

}

之后我通过电子邮件发送 CSV 文件:

Attachment data_OD = new Attachment(LeSource, MediaTypeNames.Application.Octet);
Attachment data_LV = new Attachment(LeSource_LV, MediaTypeNames.Application.Octet);
oEmail.SendingEmail(ClientID,  data_OD, data_LV);

public void SendingEmail(string CodeClient, Attachment dataOD, Attachment dataLV)
{
    try
    {
        Pers_Conf oConf = LeConf.Get_Config(CodeClient);

        MailMessage omail = new MailMessage();
        var oSmtp = new SmtpClient("smtp.gmail.com", 587)
        {
            Credentials = new NetworkCredential("xxxxxx@gmail.com", "xxxxxx"),
            EnableSsl = true
        };

        omail.From = new MailAddress("xxxxx@gmail.com");               
        omail.To.Add(oConf.EmailAddr);
        omail.Subject = "xxxxxx_" + CodeClient;
        omail.Body = CodeClient;

        omail.Attachments.Add(dataOD);
        omail.Attachments.Add(dataLV);

        oSmtp.Send(omail);
    }
    catch (Exception excThrown)
    {
        throw excThrown;
    }

似乎 StreamWriter 没有正确关闭文件，我已经尝试过这个:

    Try
    {
    StreamWriter sw = new StreamWriter(strFilePath, false);
    }
    Catch
    {
    }
    Finaly
    {
     sw.Flush();
     sw.Close();
     sw.Dispose();
}

但在 finally block 中它不识别 sw。

有什么想法吗？

PS:这行代码抛出一个异常，提示该文件正在被其他进程使用

 using (var sw = new StreamWriter(strFilePath, false))

没有关闭是因为 StreamWriter 没有正确关闭还是因为发送电子邮件正在使用这个文件？

Answer 1

假设您多次输入此代码。
无论哪种情况，您都需要调用 MailMessage 类的 MailMsg.Dispose()。否则，它会保留附件，导致文件在您下次尝试写入时被锁定。

尝试在 MailMessage 上也使用 using 语句

        try 
        { 
            Pers_Conf oConf = LeConf.Get_Config(CodeClient); 

            using(MailMessage omail = new MailMessage())
            {
                .....
                oSmtp.Send(omail); 
            }
        } 
        catch (Exception excThrown) 
        { 
            throw excThrown; 
        }