for checking number wether is same ornot

using System;

public class IsNumberSample {
    public static void Main() {
        string str = "non-numeric";

        Console.WriteLine(Char.IsNumber('8'));      // Output: "True"
        Console.WriteLine(Char.IsNumber(str, 3));   // Output: "False"
    }
}

using System.Text.RegularExpressions; 
....
string comparestring = "888555"; 
string ourstring ="whatever string characters or numbers! like aaabbb or 888555"
string newstring = Regex.Match(ourstring, @"[\d]*").Value;
if(comparestring == newstring )
{
textbox1.text = newstring;
} 
//your result = 888555