C# Online Compiler | .NET Fiddle

using System; 
using System.Linq; 
using System.Text.RegularExpressions; 
using System.Diagnostics; 
					
public class Program
{
	public static void Main()
	{
      
		Console.WriteLine("Parsing string '123as456'\n"); 
        Stopwatch sw = new Stopwatch(); 
		sw.Start(); 
		//regex get all numbers
		Console.WriteLine(string.Format("{0:00} regex split all numbers", string.Join(null,Regex.Split("123as456", "[^\\d]"))));
	 	sw.Stop(); 
		Console.WriteLine(string.Format("								﹂ in {0} ticks",sw.ElapsedTicks.ToString("N0"))); 
		sw.Restart(); 
		//regex get all numbers 
		Console.WriteLine(string.Format("{0:00} regex replace all numbers", Regex.Replace("123as456", @"\D","")));
		sw.Stop(); 
		Console.WriteLine(string.Format("								﹂ in {0} ticks",sw.ElapsedTicks.ToString("N0"))); 
		sw.Restart();
		//regex get 1st numbers
		Console.WriteLine(string.Format("{0:00} regex match 1st number", Regex.Match("123as456", @"^\d+").ToString())); 
		sw.Stop(); 
		Console.WriteLine(string.Format("							﹂ in {0} ticks",sw.ElapsedTicks.ToString("N0"))); 
		sw.Restart();			
		//regex get last number
		Console.WriteLine(string.Format("{0:00} regex match last number ", Regex.Match("123as456", @"\d+$").ToString())); 
		sw.Stop(); 
		Console.WriteLine(string.Format("							﹂ in {0} ticks",sw.ElapsedTicks.ToString("N0"))); 
		sw.Restart();
		Console.WriteLine("Parsing string '222star10bucks'\n"); 
		//linq all numbers in a string successively 
		Console.WriteLine( 
			string.Format("{0:00} linq select all numbers where long format", 
			   new string(
				         (from t in "222star10bucks"
                  		  where char.IsDigit(t)
                  		  select t).ToArray()
			             )
						 )
		                 );
		
		 sw.Stop(); 
		 Console.WriteLine(string.Format("												﹂ in {0} ticks",sw.ElapsedTicks.ToString("N0"))); 
		 sw.Restart();
		 //linq all numbers in a string successively 
	     Console.WriteLine(string.Format("{0:00} linq where digits all numbers", new String("222star10bucks".Where(Char.IsDigit).ToArray()))); 
		 sw.Stop(); 
		 Console.WriteLine(string.Format("									﹂ in {0} ticks",sw.ElapsedTicks.ToString("N0"))); 
		 sw.Restart();
         //linq 1st number in a string    		
		 Console.WriteLine(string.Format("{0:00} linq takewhile 1st number", new String("222star10bucks".TakeWhile(Char.IsDigit).ToArray()))); 
         sw.Stop(); 
		 Console.WriteLine(string.Format("								﹂ in {0} ticks",sw.ElapsedTicks.ToString("N0"))); 
		 sw.Restart();  		
		 //linq last number in a string, must end in a number
		 Console.WriteLine(string.Format("{0:00} linq reverse takewhile last number", string.Concat("222star10".ToArray().Reverse().TakeWhile(char.IsNumber).Reverse())));
		 sw.Stop(); 
		 Console.WriteLine(string.Format("									﹂ in {0} ticks",sw.ElapsedTicks.ToString("N0"))); 
		
	}
}

         Console.WriteLine(string.Format("{0:00} linq reverse takewhile last number", string.Concat("222star10".ToArray().Reverse().TakeWhile(char.IsNumber).Reverse())));
 
using System; 
using System.Linq; 
using System.Text.RegularExpressions; 
using System.Diagnostics; 
                    
public class Program
{
    public static void Main()
    {
      
        Console.WriteLine("Parsing string '123as456'\n"); 
        Stopwatch sw = new Stopwatch(); 
        sw.Start(); 
        //regex get all numbers
        Console.WriteLine(string.Format("{0:00} regex split all numbers", string.Join(null,Regex.Split("123as456", "[^\\d]"))));
        sw.Stop(); 
        Console.WriteLine(string.Format("                               ﹂ in {0} ticks",sw.ElapsedTicks.ToString("N0"))); 
        sw.Restart(); 
        //regex get all numbers 
        Console.WriteLine(string.Format("{0:00} regex replace all numbers", Regex.Replace("123as456", @"\D","")));
        sw.Stop(); 
        Console.WriteLine(string.Format("                               ﹂ in {0} ticks",sw.ElapsedTicks.ToString("N0"))); 
        sw.Restart();
        //regex get 1st numbers