C#

// experimental code : written very quickly, not tested thorougly
// use at your own risk !

public class FirstLastDictionary<K, V> : Dictionary<K, V>
{
    public K firstKeyAdded { get; set; }

    public K lastKeyAdded { get; set; }

    public void Add(K theKey, V theValue)
    {
        if(firstKeyAdded == null) firstKeyAdded = theKey;

        lastKeyAdded = theKey;

        base.Add(theKey, theValue);
    }
}

private void button1_Click(object sender, EventArgs e)
{
    FirstLastDictionary<string, int> myFLdict = new FirstLastDictionary<string, int>();

    Random r = new Random();

    for (int i = 0; i < 100; i++)
    {
        int rndValue = r.Next();

        myFLdict.Add("key " + rndValue.ToString(), rndValue);

        Console.WriteLine("adding : " + rndValue);
    }

    Console.WriteLine("firstkeyadded = " + myFLdict.firstKeyAdded);
    Console.WriteLine("firstkeyadded value = " + myFLdict[myFLdict.firstKeyAdded]);

    Console.WriteLine("lastkeyadded = " + myFLdict.lastKeyAdded);
    Console.WriteLine("lastkeyadded value = " + myFLdict[myFLdict.lastKeyAdded]);
}

public class myclass
{
   workflowservicehost host = new workflowservicehost();

   public myclass(...) {}

}

public class myclass
{
   workflowservicehost host;

   public myclass(...) 
   {
      host = new workflowservicehost();
   }
}

dataminers wrote:

How can I distinguish between unary minus operator and binary minus operator in string format.

<operand><operator><operand>

<unary operator><operand>|<number>|...