ExpressionVisitor demo

CollectingPropertiesTest.cs

using System;
using System.Collections.Generic;
using System.Linq.Expressions;
using System.Reflection;
using Xunit;

namespace ClassLibrary1
{
    public class CollectingPropertiesTest
    {
        [Fact]
        public void VisitCollectsProperties()
        {
            // Fixture setup
            var sut = new CollectingProperties();
            Expression<Func<Person, string>> nameExpr = x => x.Name;
            Expression<Func<Person, int>> ageExpr = x => x.Age;

            // Exercise system
            sut.Visit(nameExpr);
            sut.Visit(ageExpr);

            // Verify outcome
            Assert.Equal(2, sut.Properties.Count);
            Assert.Equal(typeof(Person).GetProperty("Name"), sut.Properties[0]);
            Assert.Equal(typeof(Person).GetProperty("Age"), sut.Properties[1]);
        }

        public class Person
        {
            public string Name { get; set; }
            public int Age { get; set; }
        }
    }

    public class CollectingProperties : ExpressionVisitor
    {
        private List<PropertyInfo> properties = new List<PropertyInfo>();

        public IList<PropertyInfo> Properties
        {
            get { return this.properties; }
        }

        protected override Expression VisitMember(MemberExpression node)
        {
            var property = node.Member as PropertyInfo;
            if (property != null)
                this.properties.Add(property);

            return base.VisitMember(node);
        }
    }
}