批量导出为 CSV

Question

我正在处理大量约会到 csv 向用户发送通知等。我想要做的是设置一个 isProcessed 标志来表示当前行已经被处理我不知道该怎么做我当前的循环。

public void DumpTableToFile(SqlConnection connection, string tableName, string destinationFile)
    {
        using (var command = new SqlCommand("select LineType,CustomerFirstName AS 'Forename' ,CustomerLastName,Age,dob as 'Date of Birth',maritalStatus AS 'Marital Status',homePhone AS 'Home', mobileNumber AS Mobile,emailAddress AS Email,Address1 + Address2  + PostCode AS 'Address' ,employmentStatus AS Employment,occupation AS Occupation,propertyValue AS 'Property Value',mortgageBalance AS 'Mortgage Balance',balanceOnSecuredDebt AS 'Balance on secured Debt',mortgageType as 'Mortgage Type' from " + tableName, connection))
        using (var reader = command.ExecuteReader())
        using (var outFile = File.CreateText(destinationFile))
        {
            string[] columnNames = GetColumnNames(reader).ToArray();
            int numFields = columnNames.Length;
            outFile.WriteLine(string.Join(",", columnNames));
            if (reader.HasRows)
            {
                while (reader.Read())
                {
                    string[] columnValues =
                        Enumerable.Range(0, numFields)
                                  .Select(i => reader.GetValue(i).ToString())
                                  .Select(field => string.Concat("\"", field.Replace("\"", "\"\""), "\""))
                                  .ToArray();

                    outFile.WriteLine(string.Join(",", columnValues));
                }
            }
        }

该标志称为 isProcessed，一旦通过 csv 导出，我想将其设置为 true。这样我就可以进行批量导出。它存在于同一个表约会中

编辑 1

很抱歉没有说明我希望将此标志写回到约会表中，以便在 csv 导出中吐出当前记录第二次处理。

Answer 1

执行以下步骤：

1. 为您的查询添加一个标准：WHERE NOT isProcessed，因此接下来您进行导出，只会处理未处理的记录。
2. 完成导出后，将此命令发送到数据库："UPDATE " + tableName + " SET isProcessed=true WHERE <exact same criteria as the select statement>"。这样，所有记录现在都被标记为已处理。
3. 将 TransactionScope 包装在 export-mechanisme 周围，包括。更新。这样，当某些事情发生故障时，整个操作将被回滚。
4. 在TransactionScope 周围加上一个try-catch，这样当导出失败时，CSV 文件将被删除，因此您永远不会有一半导出的批次。

你的代码会变成这样（我没有测试过）：

public void DumpTableToFile(SqlConnection connection, string tableName, string destinationFile)
{
    try
    {
        using(var transaction = new TransactionScope())
        {
            // Select all non-processed records.
            using (var command = new SqlCommand("select LineType,CustomerFirstName AS 'Forename' ,CustomerLastName,Age,dob as 'Date of Birth',maritalStatus AS 'Marital Status',homePhone AS 'Home', mobileNumber AS Mobile,emailAddress AS Email,Address1 + Address2  + PostCode AS 'Address' ,employmentStatus AS Employment,occupation AS Occupation,propertyValue AS 'Property Value',mortgageBalance AS 'Mortgage Balance',balanceOnSecuredDebt AS 'Balance on secured Debt',mortgageType as 'Mortgage Type' from " + tableName 
                + " WHERE NOT isProcessed", connection))
            using(var reader = command.ExecuteReader())
            using(var outFile = File.CreateText(destinationFile))
            {
                string[] columnNames = GetColumnNames(reader).ToArray();
                int numFields = columnNames.Length;
                outFile.WriteLine(string.Join(",", columnNames));
                if (reader.HasRows)
                {
                    while(reader.Read())
                    {
                        string[] columnValues =
                            Enumerable.Range(0, numFields)
                                .Select(i => reader.GetValue(i).ToString())
                                .Select(field => string.Concat("\"", field.Replace("\"", "\"\""), "\""))
                                .ToArray();

                        outFile.WriteLine(string.Join(",", columnValues));
                    }
                }
            }

            // Update the same records that were just exported.
            using (var command = new SqlCommand("UPDATE " + tableName + " SET isProcessed=true WHERE NOT isProcessed", connection))
                command.ExecuteNonQuery();

            transaction.Complete();
        }
    }
    catch
    {
        // If something went wrong, delete the export file.
        File.Delete(destinationFile);
        throw;
    }
}