如何在源代码编译的Regex中指定超时值？

你可以通过两种方式为源代码生成的Regex添加超时：

1. 在GeneratedRegex属性中预设超时（.NET 7及以上） #

直接在GeneratedRegex属性里指定Timeout参数，生成的Regex实例会默认使用该超时值，后续调用Match时无需额外传参：

[GeneratedRegex(@"^[0-9A-Z]([-.\w]*[0-9A-Z])*$", RegexOptions.IgnoreCase, Timeout = "00:00:00.100")]
private static partial Regex Pattern();

private static readonly Regex SCPattern = Pattern();

此时调用SCPattern.Match(input)会自动应用100毫秒的超时，超时后会抛出RegexMatchTimeoutException。

2. 使用带超时参数的Match重载 #

不管.NET版本，都可以直接调用Regex.Match的重载方法，显式传入超时值：

Match m = SCPattern.Match(input, 0, TimeSpan.FromMilliseconds(100));

这里第二个参数0表示从输入字符串的起始位置开始匹配，你可以根据需求调整。

修改后的最小可复现代码示例 #

using System.Diagnostics;
using System.Text.RegularExpressions;

public partial class Program
{
    // 方法1：在属性中预设超时
    [GeneratedRegex(@"^[0-9A-Z]([-.\w]*[0-9A-Z])*$", RegexOptions.IgnoreCase, Timeout = "00:00:00.100")]
    private static partial Regex PatternWithTimeout();

    private static readonly Regex SCPatternWithTimeout = PatternWithTimeout();

    // 方法2：使用默认生成，调用时传超时
    [GeneratedRegex(@"^[0-9A-Z]([-.\w]*[0-9A-Z])*$", RegexOptions.IgnoreCase)]
    private static partial Regex Pattern();

    private static readonly Regex SCPattern = Pattern();

    public static void Main()
    {
        Stopwatch sw;
        string[] addresses = { "AAAAAAAAAAAAaaaaaaaaaaaa!@contoso.com" };
        string input;

        foreach (var address in addresses)
        {
            string mailBox = address[..address.IndexOf('@')];
            int index = 0;

            // 测试预设超时的源代码生成Regex
            index = 0;
            Console.WriteLine("source-compiled regex with preset timeout:");
            for (int ctr = mailBox.Length - 1; ctr >= 0; ctr--)
            {
                index++;
                input = mailBox.Substring(ctr, index);

                sw = Stopwatch.StartNew();
                try
                {
                    Match m = SCPatternWithTimeout.Match(input);
                    sw.Stop();
                    if (m.Success)
                        Console.WriteLine("{0,2}. Matched '{1,27}' in {2}",
                                        index, m.Value, sw.Elapsed);
                    else
                        Console.WriteLine("{0,2}. Failed  '{1,27}' in {2}",
                                        index, input, sw.Elapsed);
                }
                catch (RegexMatchTimeoutException)
                {
                    sw.Stop();
                    Console.WriteLine("{0,2}. Timeout '{1,27}' in {2}",
                                    index, input, sw.Elapsed);
                }
            }
            Console.WriteLine();

            // 测试调用时传超时的源代码生成Regex
            index = 0;
            Console.WriteLine("source-compiled regex with explicit timeout:");
            for (int ctr = mailBox.Length - 1; ctr >= 0; ctr--)
            {
                index++;
                input = mailBox.Substring(ctr, index);

                sw = Stopwatch.StartNew();
                try
                {
                    Match m = SCPattern.Match(input, 0, TimeSpan.FromMilliseconds(100));
                    sw.Stop();
                    if (m.Success)
                        Console.WriteLine("{0,2}. Matched '{1,27}' in {2}",
                                        index, m.Value, sw.Elapsed);
                    else
                        Console.WriteLine("{0,2}. Failed  '{1,27}' in {2}",
                                        index, input, sw.Elapsed);
                }
                catch (RegexMatchTimeoutException)
                {
                    sw.Stop();
                    Console.WriteLine("{0,2}. Timeout '{1,27}' in {2}",
                                    index, input, sw.Elapsed);
                }
            }
        }

        Console.WriteLine("Press any key ...");
        Console.ReadKey();
    }
}

注意：处理超时场景时，需要捕获RegexMatchTimeoutException来处理超时情况。

内容的提问来源于stack exchange，提问作者Qrt