File.AppendText() 慢

Question

我有一个大文件，其结构如下：

 Report 1  section 1
 Report 2  section 1
 Report 1  section 2
 Report 3  section 1
 Report 2  section 2
 and so on....

我必须把所有的1放在一起，所有的2放在一起，依此类推，形成报表1、报表2、报表3。我别无选择，只能逐行进行。问题是它非常慢。这是我用来编写文件的代码：

        using (StreamWriter sw = File.AppendText(newFileName))
                    { sw.WriteLine(line); }

我认为问题是 File.AppendText() 正在减慢这个过程。我想知道是否有人对如何加快速度有任何想法。

Answer 1

您似乎在每次迭代时都打开该文件。试试这个：

using (StreamWriter sw = File.AppendText(path))
{
    while (condition)
    {
        sw.WriteLine("write your line here");
    }
}

正如 Chris Berger 评论的那样，您可以像这样嵌套使用

using (StreamWriter sw1 = File.AppendText(path1))
{
    using (StreamWriter sw2 = File.AppendText(path2))
    {
        while (condition)
        {
            if(writeInFile1)
                sw1.WriteLine("write your line here");
            else
                sw2.WriteLine("write your line here");
        }
    }
}

Answer 2

正如您在

中提到的

This is a good solution however I will have five or six report files coming from one file...

您可以使用多个 using 语句一次打开所有 6 个文件。

using (StreamReader sr = File.OpenText(source)
using (StreamWriter sw1 = File.AppendText(path1))
using (StreamWriter sw2 = File.AppendText(path2))
using (StreamWriter sw3 = File.AppendText(path3))
using (StreamWriter sw4 = File.AppendText(path4))
using (StreamWriter sw5 = File.AppendText(path5))
using (StreamWriter sw6 = File.AppendText(path6))
{
    string line;
    while ((line = sr.ReadLine()) != null)
    {
        if(line.StartsWith("Report 1")
        {
            sw1.WriteLine(line);
        }
        else if(line.StartsWith("Report 2")
        {
            sw2.WriteLine(line);
        }
        else if(line.StartsWith("Report 3")
        {
            sw3.WriteLine(line);
        }
        else if(line.StartsWith("Report 4")
        {
            sw4.WriteLine(line);
        }
        else if(line.StartsWith("Report 5")
        {
            sw5.WriteLine(line);
        }
        else if(line.StartsWith("Report 6")
        {
            sw6.WriteLine(line);
        }
        else
        {
            throw new InvalidDataException($"Line does not start with a report number: \n{line}");
        }
    }
}

File.AppendText() 慢

File.AppendText() Slow

c#

streamwriter