public virtual ODataExpression VisitUnary(ODataUnaryExpression expr)
 {
     ODataExpression operand = this.Visit(expr.Operand);
     if (operand != expr.Operand)
     {
         return new ODataUnaryExpression(operand, expr.ExpressionType);
     }
     return this.Visit(expr);
 }
 public override ODataExpression VisitUnary(ODataUnaryExpression expr)
 {
     switch (expr.ExpressionType)
     {
         case ExpressionType.Not:
             this.sqlBuilder.Append("NOT ");
             this.Visit(expr.Operand);
             break;
         case ExpressionType.Negate:
             this.sqlBuilder.Append("-");
             this.Visit(expr.Operand);
             break;
         default:
             throw new NotSupportedException();
     }
     return expr;
 }