C#

double binToHex=(0*Math.Pow(2,3))+(1*Math.Pow(2,2))+(0*Math.Pow(2,1))+(1*Math.Pow(2,0));

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"When the only tool you have is a hammer, a sore thumb you will have."

public void BuildTree(DataSet ds)
{
  // Don't forget error checking throughout this code!
  DataRow[] roots = ds.Table[0].Select("ParentID = 0 OR ParentID IS NULL");
  foreach (DataRow root in roots)
  {
    BuildTreeHelper(root, myTreeView.Nodes);
  }
}
public void BuildTreeHelper(DataRow row, TreeNodeCollection nodes)
{
  TreeNode node = CreateNodeFromData(row);
  nodes.Add(node);

  DataRow[] rows = row.Table.Select("ParentID = " + node.Tag);
  foreach (DataRow row in rows)
    BuildTreeHelper(row, node.Nodes);
}
public TreeNode CreateNodeFromData(DataRow row)
{
  TreeNode node = new TreeNode();
  node.Text = row["Name"];
  node.Tag = row["ID"];
  // Whatever...

  return node;
}