string s =""; 
 

 
     System.Net.IPAddress[] addressList = Dns.GetHostByName(Dns.GetHostName()).AddressList; 
 

 
     for (int i = 0; i < addressList.Length; i ++) 
 
     { 
 
          s += addressList[i].ToString() + "\n"; 
 
     } 
 

 
     textBox1.Text = s;