C#

lock(_lockObj)
{
   Console.WriteLine("hello!");
}

System.Threading.Monitor.Enter(_lockObj);
try
{
    Console.WriteLine("hello");
}
finally
{
    System.Threading.Monitor.Exit(_lockObj);
}

public class MySingleton
{
  #region Singleton Pattern
  private static volatile MySingleton m_instance;
  private static object m_syncRoot = new object(); // lock target

  public static MySingleton
  {
    get
    {
      if (m_instance == null)
      {
        // Lock the syncroot object, rather than typeof(MySingleton)
        lock (m_syncRoot)
        {
          if (m_instance == null)
          {
            m_instance = new MySingleton();
          }
        }
      }

      return m_instance;
    }
  }
  #endregion
}

public class MyCollection: CollectionBase
{
  private class MySyncCollection: MyCollection
  {
    internal MySyncCollection(MyCollection col)
    {
      m_col = col;
      m_root = col.SyncRoot;
    }

    private MyCollection m_col;
    private object m_root;

    public override object SyncRoot
    {
      get
      {
        return m_root;
      }
    }

    public int Add(object item)
    {
      int index;
      lock (m_root)
      {
        index = m_col.Add(item);
      }
      return index;
    }

    // ... Override other methods ...
  }

  private object m_syncRoot = new object();  // lock target

  public override object SyncRoot
  {
    get
    {
      m_syncRoot;
    }
  }

  public int Add(object item)
  {
    return List.Add(item);
  }

  public static MyCollection Synchronized(MyCollection col)
  {
    if (col == null)
      throw new ArgumentNullException("The specified collection is null. Can not synchronize a non-existent collection.");

    return new MyCollection.MySyncCollection(col);
  }

  // ... Other methods ...
}

<code>
public int CountNodes(Node n)
{
    if(ExitCondition)    // what's your exit condition?
    {
        return ?;        // what should you return for your base 
case?
    }
    else
    {
    // what do you need to return here. What are you going to pass to the recursive call?
        return ? + CountNodes(?);     
    } 
}
</code>

while {not at end of list)
    Incrememnt counter
loop
return counter

int count(POINTER head)<br />
{<br />
	return head!=NULL ? count(head->next)+1 : 0 ;<br />
}