/// <summary>
 /// Construct as a nested expression entry.
 /// </summary>
 /// <param name="parent"></param>
 /// <param name="type"></param>
 /// <param name="expression"></param>
 public FilterExpressionEntry(FilterExpression parent, FilterExpression.SearchType type, FilterExpression expression)
 {
     Parent     = parent;
     Type       = type;
     Operation  = null;
     Expression = expression;
 }
 /// <summary>
 /// Constructor
 /// </summary>
 /// <param name="left"></param>
 /// <param name="right"></param>
 /// <param name="op"></param>
 /// <param name="type"></param>
 public FilterExpressionOperation(String left, String right, FilterExpression.SearchOperator op, FilterExpression.SearchType type)
 {
     Left     = left;
     Right    = right;
     Operator = op;
     Type     = type;
 }