Here is a method to pass class property of value type into method which updates the value of that property. Instead of specifying object instance and property name as a string (which is error prone), it uses LinQ expression. Similar technique is used by Fluent NHibernate to define mappings between database table and .NET class

using System;
using System.Linq.Expressions;
using System.Reflection;

namespace ConsoleTest
{
    public class Values
    {
        public int X { get; set; }
        public int Y { get; set; }

        public override string ToString()
        {
            return String.Format("[ X={0} Y={1} ]", X, Y);
        }
    }

    class Program
    {
        static void Main()
        {
            var values = new Values {X = 1, Y = 1};

            // pass parameter to be incremented as linq expression
            IncrementValue(values, v => v.X);
            IncrementValue(values, v => v.X);
            IncrementValue(values, v => v.Y);

            // Output is: [ X=3 Y=2 ]
            Console.Write(values);
        }

        private static void IncrementValue<T>(T obj, Expression<Func<T,int>> property)
        {
            var memberExpression = (MemberExpression)property.Body;
            var propertyInfo = (PropertyInfo)memberExpression.Member;
            // read value with reflection
            var value = (int)propertyInfo.GetValue(obj, null);
            // set value with reflection
            propertyInfo.SetValue(obj, ++value, null);
        }
    }
}