C#

using System;
using System.Collections;
using System.IO;
 
public class NameValuePair : IComparable
{
  string name;
  string value;
  public NameValuePair(string pair)
  {
    if (pair == null) throw new ArgumentNullException("pair");
    string[] arr = pair.Split('=');
 
    if (arr.Length != 2) throw new ArgumentException("Invalid format.", "pair");
    name = arr[0].Trim();
    value = arr[1].Trim();
  }
 
  public string Name
  {
    get { return name; }
    set { name = value; }
  }
 
  public string Value
  {
    get { return value; }
    set { this.value = value; }
  }
 
  public override string ToString()
  {
    return name + "=" + value;
  }
 
  int IComparable.CompareTo(object obj)
  {
    NameValuePair pair = obj as NameValuePair;
    if (pair != null)
    {
      int retval = string.Compare(name, pair.name);
      if (retval == 0)
        retval = string.Compare(value, pair.value);
 
      return retval;
    }
 
    return 1;
  }
 
  static void Main()
  {
    UniqueList list = new UniqueList();
    string[] values = new string[]
    {
      "Australia=Canberra",
      "Austria=Wiena",
      "Canada=Toronto",
      "Canada=Ottawa",
      "Austria=Wiena"
    };
 
    foreach (string value in values)
    {
      try
      {
        NameValuePair pair = new NameValuePair(value);
        list.Add(pair);
      }
      catch
      {
        Console.Error.WriteLine(@"""{0}"" is not unique", value);
      }
    }
 
    Console.WriteLine("The list contains:");
    list.Print(Console.Out);
  }
}
 
class UniqueList : ArrayList
{
  public override int Add(object value)
  {
    int pos = BinarySearch(value, Comparer.Default);
    if (pos >= 0) throw new ArgumentException("Not unique", "value");
 
    return base.Add(value);
  }
 
  internal void Print(TextWriter writer)
  {
    foreach (object value in this)
      writer.WriteLine(value);
  }
}

public class IDGenerator
{
    int min, max;

    Random r = new Random(unchecked((int)DateTime.Now.Ticks));

    public IDGenerator ()
    {
        this.min = 1000000;
        this.max = 9999999;
    }

    public string GetID ()
    {
        // Produce a number from min through max.
        // Use the RNG created at the class level.
        String myNumber = r.Next(min,max).ToString("0000000");
        return myNumber;
    }
}

int min = 1000000, max = 9999999;
Random r = new Random();
for(int i = 0; i < 5; i++)
{
    Console.WriteLine(r.Next(min, max));
}