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TinyLisp: A Language and Parser to See LINQ Expressions in Action

, 12 Jun 2010
A small program that parses expressions and evaluates them using LINQ Expressions
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;

namespace TinyLisp {
    //  Adapter to ease binding to WPF. Main goal was to create an IEnumerable of childnodes
    public class ExpressionAdapter {

        // private fields.
        private Expression _Expr;
        private string _ParentPropertyName;

        // constructor
        public ExpressionAdapter(Expression Expr, string ParentPropertyName) {
            _Expr = Expr;
            _ParentPropertyName = ParentPropertyName;
        }

        // Returns string with information about the current Property - Expression pair
        public string Text {
            get {
                if (_Expr is ConstantExpression) {
                    ConstantExpression ce = _Expr as ConstantExpression;
                    return _ParentPropertyName + " = " + (_Expr == null ? "null" : (_Expr.NodeType.ToString() + "  " + ce.Value));
                } else {

                    return _ParentPropertyName + " = " + (_Expr == null ? "null" : (_Expr.NodeType.ToString()));
                }
            }
        }

        // Returns all properties of type Expression as an IEnumerable<ExpressionAdapter>
        public IEnumerable<ExpressionAdapter> Children {
            get {
                if (_Expr == null) return null;
                else
                    return from childExpression in _Expr.GetType().GetProperties().OrderBy(p=>p.Name)
                           where childExpression.PropertyType == typeof(Expression)
                           select new ExpressionAdapter((Expression)childExpression.GetValue(_Expr, null), childExpression.Name);
            }
        }
    }
}

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License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

gjvdkamp
Leaseplan Corporation
Netherlands Netherlands
Gert-Jan is a Senior Quantitative Risk Manager at Leaseplan Corporation. In that job he doesn't get to code much he does these little projects to keep his skills up and feed the inner geek.
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