c# - Out of memory异常读写文本文件

Question

我在执行以下代码几秒钟后遇到内存不足异常。在抛出异常之前它不写任何东西。该文本文件的大小约为 0.5 GB。我正在编写的文本文件最终也将是大约 3/4 千兆字节。有什么技巧可以绕过这个异常吗？我认为这是因为文本文件太大。

public static void ToCSV(string fileWRITE, string fileREAD)
{
    StreamWriter commas = new StreamWriter(fileWRITE);
    var readfile = File.ReadAllLines(fileREAD);


    foreach (string y in readfile)
    {

        string q = (y.Substring(0,15)+","+y.Substring(15,1)+","+y.Substring(16,6)+","+y.Substring(22,6)+ ",NULL,NULL,NULL,NULL");
        commas.WriteLine(q);
    }

    commas.Close();
}

我已将我的代码更改为以下内容，但我仍然得到相同的异常？

public static void ToCSV(string fileWRITE, string fileREAD)
{
    StreamWriter commas = new StreamWriter(fileWRITE);

    using (FileStream fs = File.Open(fileREAD, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
    using (BufferedStream bs = new BufferedStream(fs))
    using (StreamReader sr = new StreamReader(bs))
    {
        string y;
        while ((y = sr.ReadLine()) != null)
        {
            string q = (y.Substring(0, 15) + "," + y.Substring(15, 1) + "," + y.Substring(16, 6) + "," + y.Substring(22, 6) + ",NULL,NULL,NULL,NULL");
            commas.WriteLine(q);
        }
    }

    commas.Close();
}

Answer 1

逐行读取文件，这将帮助您避免OutOfMemoryException。我个人更喜欢使用 using 来处理流。它确保在出现异常时关闭文件。

public static void ToCSV(string fileWRITE, string fileREAD)
{
    using(var commas = new StreamWriter(fileWRITE))
    using(var file = new StreamReader("yourFile.txt"))
    {
        var line = file.ReadLine();

        while( line != null )
        { 
            string q = (y.Substring(0,15)+","+y.Substring(15,1)+","+y.Substring(16,6)+","+y.Substring(22,6)+ ",NULL,NULL,NULL,NULL");
            commas.WriteLine(q);
            line = file.ReadLine();
        }
    } 
}