尝试启用match whole word选项沿着regex (\d)*一起

不是那么有效的解决方案，但可能也在工作：

using System;
using System.Linq;
using System.Collections.Generic;

namespace Demo
{
    class Program
    {
        static readonly char[] numbers = new char[] {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9'};
        static readonly char[] allowedChars = new char[] {'(', ')', '{', '}', '[', ']', ' '};
        public static void Main(string[] args)
        {
            const string input = @"
Margin = new Thickness(10);
int i = 10;
Margin = margin123;
int i100 = j100;
a10
124b
";
            List<string> matches = new List<string>();
            foreach (var row in input.Split('\n')) 
            {
                int start = row.IndexOfAny(numbers);
                
                if (start == -1) 
                    continue;
                
                if (start == 0 || numbers.Contains(row[start - 1]) || allowedChars.Contains(row[start - 1]))
                {
                    matches.Add(row);
                } 
            }
            
            Console.WriteLine(string.Join("\n\r", matches));
            Console.ReadKey(true);
        }
    }
}

输出：

Margin = new Thickness(10);
int i = 10;
124b