在 C# 中打印一行上方的第一行

Question

我有一个文本文件，它包含 8000 多行。我需要打印一个特定的行，并打印另一行，这是第一行的前一行。问题是第二行没有 uniqe 功能，所以我不能像调用第一行那样调用它。

总结

：

- 第二行

- 第一行

：

如何使用第一行获得第二行？

我知道我应该反制线条并捕获第二行，但我不知道如何。我很感激任何形式的帮助。

Answer 1

我用一堆行创建了一个 .txt 文件，中间埋了两行，第一行是“弗兰克”，第二行是“球”。要打印“弗兰克球”试试这个：string line;        string line1;        string line2;        System.IO.StreamReader file = new System.IO.StreamReader(@"c:\test.txt");        //walk the file line by line        while ((line = file.ReadLine()) != null)        {            if(line.Contains("Ball"))            {                //Once you find your search value, set line2 to the line and stop walking the file.                line2 = line;                break;            }            //set line1 to the line value to hold onto it if you find your search value            line1 = line;        }       //Now you have both strings and you can concatenate them however you want and print them        string s = line1 + " " + line2;        PrintDocument p = new PrintDocument();        p.PrintPage += delegate (object sender1, PrintPageEventArgs e1)        {            e1.Graphics.DrawString(s, new Font("Times New Roman", 12), new SolidBrush(Color.Black), new RectangleF(0, 0, p.DefaultPageSettings.PrintableArea.Width, p.DefaultPageSettings.PrintableArea.Height));        };        try        {            p.Print();        }        catch (Exception ex)        {            throw new Exception("Exception Occured While Printing", ex);        }        file.Close();

Answer 2

static string GetPreviousLine(string[] lines){    string temp = "";    foreach (string line in lines)    {        if (line == "First Line") return temp;        else temp = line;    }    throw new Exception("not found");}我们阅读每一行并将其保存到temp. 然后我们阅读下一行，如果是line 1，我们知道那temp是line 2，否则我们将新行保存到temp并以相同的方式继续。

Answer 3

我知道我应该反制线条并捕获第二行，但我不知道如何。要计算行数，您可以简单地对方法返回for的lines数组使用循环System.IO.File.ReadAllLines(filePath)。这将在每次迭代时递增，您可以使用lines[i - 1].这是一个使用for循环搜索字符串数组的方法，查找与特定字符串匹配的行（在本例中不区分大小写），如果找到搜索词，则返回前一个数组项：private static string GetLineBefore(string lineToFind, string[] lines){&nbsp; &nbsp; // Argument validation to avoid NullReferenceException or unnecessary search&nbsp; &nbsp; if (lines != null && !string.IsNullOrEmpty(lineToFind))&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; // Start at the second line (index 1) since there is no line before the first&nbsp; &nbsp; &nbsp; &nbsp; for (int i = 1; i < lines.Length; i++)&nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; if (lines[i].Equals(lineToFind, StringComparison.OrdinalIgnoreCase))&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // Since 'i' represents the index of the first line that we were&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; // searching for, we return the previous item, at index 'i - 1'&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; return lines[i - 1];&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }&nbsp; &nbsp; // If we never found our first line, return null to indicate no results&nbsp; &nbsp; return null;}你可以这样称呼它：var filePath = @"f:\public\temp\temp.txt";var searchLine = "This is the text for the first line that I want to find";// This will represent the line before the first one abovevar previousLine = GetLineBefore(searchLine, File.ReadAllLines(filePath));