如何从文本文件中打印随机行但排除包含某些字符的行？C＃

debugcn 发表于 Dev

AB147

我正在尝试从文件中读取行，但我想排除包含不相关字符的行。我只想打印包含字母字符的行。此外，一旦打印了一行，我就不想再次打印它。这是我当前的代码：

`string[] lines = System.IO.File.ReadAllLines(@"File Location");  //Create line array..
Random rnd1 = new Random(); //Random value

Console.ReadKey();

Console.WriteLine("Contents of file.txt:");
foreach (string line in lines)
{
Console.WriteLine(lines[rnd1.Next(lines.Length)]); //Print random line
}

鲁弗斯

一种方法是在您从文件中读取行时过滤这些行。我们可以通过将每一行视为字符数组来做到这一点，通过将可接受的非字母数字字符作为 an 传递IEnumerable给Linq扩展方法来排除可接受的非字母数字字符.Except()，然后我们可以.All通过调用结构体的IsLetter方法来测试其余字符是否为字母char（如果字符是字母则返回真）。

例如：

Random random = new Random();

static void Main()
{
    // Valid non-alphanumeric characters are stored in this list.
    // Currently this is only a space, but you can add other valid
    // punctuation here (periods, commas, etc.) if necessary.
    var validNonAlphaChars = new List<char> {' '};

    // Get all lines that contain only letters (after
    // excluding the valid non-alpha characters).
    var fileLines = File.ReadAllLines(@"c:\temp\temp.txt")
        .Where(line => line.Except(validNonAlphaChars).All(char.IsLetter))
        .ToList();

    // Shuffle the lines so they're in a random order using the Fisher-Yates
    // algorithm (https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle)
    for (int i = 0; i < fileLines.Count; i++)
    {
        // Select a random index after i
        var rndIndex = i + random.Next(fileLines.Count - i);

        // Swap the item at that index with the item at i
        var temp = fileLines[rndIndex];
        fileLines[rndIndex] = fileLines[i];
        fileLines[i] = temp;
    }

    // Now we can output the lines sequentially from fileLines
    // and the order will be random (and non-repeating)
    fileLines.ForEach(Console.WriteLine);

    GetKeyFromUser("\nPress any key to exit...");
}

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