Répéter un Caractère x fois

using System; 
using System.Collections.Generic; 
using System.ComponentModel; 
using System.Data; 
using System.Drawing; 
using System.Linq; 
using System.Text; 
using System.Text.RegularExpressions; 
using System.Windows.Forms; 

using Helpers;

String Ma = this.M1.Text;

String Ma = this.M1.Text.CreateSublevelMask();

string pattern = "0"; 
int count = Regex.Matches(bcbinaire, pattern).Count; 

string pattern1 = "0"; 
int count1 = Regex.Matches(bcbinaire1, pattern1).Count; 

string pattern2 = "0"; 
int count2 = Regex.Matches(bcbinaire2, pattern2).Count; 

string pattern3 = "0"; 
int count3 = Regex.Matches(bcbinaire3, pattern3).Count; 

string pattern = "0"; 
int count = Regex.Matches(bcbinaire, pattern).Count; 
int count1 = Regex.Matches(bcbinaire1, pattern).Count;  
int count2 = Regex.Matches(bcbinaire2, pattern).Count; 
int count3 = Regex.Matches(bcbinaire3, pattern).Count; 

// Calcul Subnet Apres conversion d'une chaine en Byte + erreur si Chiffre incorrecte 

String IPa = this.IP1.Text; 
String Ma = this.M1.Text; 
Byte ip1 = Convert.ToByte(IPa); 
Byte m1 = Convert.ToByte(Ma); 
Byte subnet1 = (byte)(ip1 & m1); 
Sub1.Text = Convert.ToString(subnet1); 

String IPb = this.IP2.Text; 
String Mb = this.M2.Text; 
Byte ip2 = Convert.ToByte(IPb); 
Byte m2 = Convert.ToByte(Mb); 
Byte subnet2 = (byte)(ip2 & m2); 
Sub2.Text = Convert.ToString(subnet2); 

string IPc = this.IP3.Text; 
string Mc = this.M3.Text; 
Byte ip3 = Convert.ToByte(IPc); 
Byte m3 = Convert.ToByte(Mc); 
byte subnet3 =(byte)(ip3 & m3); 
Sub3.Text = Convert.ToString(subnet3); 


string IPd = this.IP4.Text; 
string Md = this.M4.Text; 
Byte ip4 = Convert.ToByte(IPd); 
Byte m4 = Convert.ToByte(Md); 
Byte subnet4 =(byte)(ip4 & m4); 
Sub4.Text = Convert.ToString(subnet4); 


// Calcule BroadCastApres avoir inverser le masque 

int mbc = Convert.ToInt32(Ma); 
int mbc1 = Convert.ToInt32(Mb); 
int mbc2 = Convert.ToInt32(Mc); 
int mbc3 = Convert.ToInt32(Md); 

string bcbinaire = Convert.ToString(mbc, 2).PadLeft(8, '0'); 
string bcbinaire1 = Convert.ToString(mbc1, 2).PadLeft(8, '0'); 
string bcbinaire2 = Convert.ToString(mbc2, 2).PadLeft(8, '0'); 
string bcbinaire3 = Convert.ToString(mbc3, 2).PadLeft(8, '0'); 

byte reverse_mbc = Convert.ToByte(new string(Convert.ToString(mbc, 2).PadLeft(8, '0').Reverse().ToArray()), 2); 
byte reverse_mbc1 = Convert.ToByte(new string(Convert.ToString(mbc1, 2).PadLeft(8, '0').Reverse().ToArray()), 2); 
byte reverse_mbc2 = Convert.ToByte(new string(Convert.ToString(mbc2, 2).PadLeft(8, '0').Reverse().ToArray()), 2); 
byte reverse_mbc3 = Convert.ToByte(new string(Convert.ToString(mbc3, 2).PadLeft(8, '0').Reverse().ToArray()), 2); 

Byte Broad1 = (byte)(ip1 | ~mbc); bc1.Text = Convert.ToString(Broad1); 
Byte Broad2 = (byte)(ip2 | ~mbc1); bc2.Text = Convert.ToString(Broad2); 
Byte Broad3 = (byte)(ip3 | ~mbc2); bc3.Text = Convert.ToString(Broad3); 
Byte Broad4 = (byte)(ip4 | ~mbc3); bc4.Text = Convert.ToString(Broad4); 

//Calcul premier address dispo 
pad1.Text = Sub1.Text; pad2.Text = Sub2.Text; pad3.Text = Sub3.Text; 
int padcalcul = Convert.ToInt32(subnet4); 
int padcalcul1 = padcalcul + 1; 
string returnpad = Convert.ToString(padcalcul1); 
pad4.Text = returnpad; 

//Calcul derniere adress dispo 
dad1.Text = bc1.Text; dad2.Text = bc2.Text; dad3.Text = bc3.Text; 
int dadcalcul = Convert.ToInt32(Broad4); 
int dadcalcul1 = dadcalcul - 1; 
string returndad = Convert.ToString(dadcalcul1); 
dad4.Text = returndad; 

//compte le nombre de 0 dans le masque via une Expression Reguliere de Type Regular(string , string) 

string pattern = "0"; 
int count = Regex.Matches(bcbinaire, pattern).Count; 

string pattern1 = "0"; 
int count1 = Regex.Matches(bcbinaire1, pattern1).Count; 

string pattern2 = "0"; 
int count2 = Regex.Matches(bcbinaire2, pattern2).Count; 

string pattern3 = "0"; 
int count3 = Regex.Matches(bcbinaire3, pattern3).Count; 

int addnb0 = count + count1 + count2 + count3; 

int nbreseau = (int)Math.Pow(2, addnb0); 
nbr.Text = Convert.ToString(nbreseau); 

int nbreseau1 = nbreseau - 2; 
nbru.Text = Convert.ToString(nbreseau1); 

private void ConvertToSubnet(string ip_addr, string mask, out byte ip, out byte m, out byte subnet)
{
    ip = Convert.ToByte(ip_addr);
	m = Convert.ToByte(mask.CreateSublevelMask());
	subnet = (byte)(ip & m);
}

private void ComputeBroadcast(byte ip, string mask, out byte broad, out string bcbBinaire)
{
   int mbc = Convert.ToInt32(mask);
   bcbBinaire = Convert.ToString(mbc, 2).PadLeft(8, '0');
   byte reverseMbc = Convert.ToByte(Convert.ToString(mbc, 2).PadLeft(8, '0').Reverse().ToArray(), 2);
   broad = (byte)(ip | ~mbc);
}

private int Count(string bcbBinaire, string pattern)
{
    return Regex.Matches(bcbBinaire, pattern).Count;
}

private void Button_Click(object sender, EventArgs e)
{
   byte ip;
   byte m;
   byte subnet;
   byte broad;
   string bcbBinaire;
   int totalCount = 0;

   ConvertToSubnet(IP1.Text, M1.Text, out ip, out m, out subnet);
   ComputeBroadcast(ip, M1.Text, out broad, out bcbBinaire); 
   bc1.Text = broad.ToString();
   Sub1.Text = subnet.ToString();
   totalCount += Count(bcbBinaire, "0");

   ConvertToSubnet(IP2.Text, M2.Text, out ip, out m, out subnet);
   ComputeBroadcast(ip, M2.Text, out broad, out bcbBinaire); 
   bc2.Text = broad.ToString();
   Sub2.Text = subnet.ToString();
   totalCount += Count(bcbBinaire, "0");

   ConvertToSubnet(IP3.Text, M3.Text, out ip, out m, out subnet);
   ComputeBroadcast(ip, M3.Text, out broad, out bcbBinaire); 
   bc2.Text = broad.ToString();
   Sub3.Text = subnet.ToString();
   totalCount += Count(bcbBinaire, "0");

   ConvertToSubnet(IP4.Text, M4.Text, out ip, out m, out subnet);
   ComputeBroadcast(ip, M4.Text, out broad, out bcbBinaire); 
   bc2.Text = broad.ToString();
   Sub4.Text = subnet.ToString();
   totalCount += Count(bcbBinaire, "0");

   //Calcul premier address dispo 
   pad1.Text = Sub1.Text;
   pad2.Text = Sub2.Text;
   pad3.Text = Sub3.Text; 
   int padcalcul = Convert.ToInt32(subnet); 
   padcalcul++; 
   pad4.Text = padcalcul.ToString(); 

   //Calcul derniere adress dispo 
   dad1.Text = bc1.Text;
   dad2.Text = bc2.Text; 
   dad3.Text = bc3.Text; 
   int dadcalcul = Convert.ToInt32(broad); 
   dadcalcul--; 
   dad4.Text = dadcalcul1.ToString(); 
   
   int nbReseau = (int)Math.Pow(2, totalCount);
   nbr.Text = nbReseau.ToString();

   nbReseau -= 2;
   nbru.Text = nbReseau.ToString();
}