using System;

using System.Text.RegularExpressions;

​

public class Program

{

    public static void Main()

    {

        string str = "@{TotalPhysicalMemory= 17856325}";

        Regex regex = new Regex(@"^\@{TotalPhysicalMemory= (\d+)}");

        var match = regex.Match(str);

        Console.WriteLine("Value: " + match.Groups[1].Value);

    }

}