Example output for Stack Overflow question: How to simplify repeating if-then-assign construction? - http://stackoverflow.com/a/29918452/7586

ModifyExistingEntityMapping.cs

// !!!
// !!!  Do not modify this file, it is automatically generated. Change the .tt file instead.     !!!
// !!!
namespace Your.Mapper
{
    partial class Mapper
    {
        /// <summary>
        /// Set <paramref name="target"/> properties by copying them from <paramref name="source"/>.
        /// </summary>
        /// <remarks>Mapping:<br/>
        /// <see cref="Product.Name"/> → <see cref="ProductEntity.Name"/> <br/>
        /// <see cref="Product.Id"/> → <see cref="ProductEntity.ServiceId"/> <br/>
        /// </remarks>
        /// <returns><c>true</c> if any property was changed, <c>false</c> if all properties were the same.</returns>
        public bool ModifyExistingEntity(Product source, ProductEntity target)
        {
            bool dirty = false;
            if (target.Name != source.Name)
            {
                dirty = true;
                target.Name = source.Name;
            }            
            if (target.ServiceId != source.Id)
            {
                dirty = true;
                target.ServiceId = source.Id;
            }            
            return dirty;
        }
        /// <summary>
        /// Set <paramref name="target"/> properties by copying them from <paramref name="source"/>.
        /// </summary>
        /// <remarks>Mapping:<br/>
        /// <see cref="Person.Employee"/> → <see cref="DbPerson.Employee"/> <br/>
        /// <see cref="Person.Name"/> → <see cref="DbPerson.FullName"/> <br/>
        /// <see cref="Person.Addredd"/> → <see cref="DbPerson.HomeAddress"/> <br/>
        /// </remarks>
        /// <returns><c>true</c> if any property was changed, <c>false</c> if all properties were the same.</returns>
        public bool ModifyExistingEntity(Person source, DbPerson target)
        {
            bool dirty = false;
            if (target.Employee != source.Employee)
            {
                dirty = true;
                target.Employee = source.Employee;
            }            
            if (target.FullName != source.Name)
            {
                dirty = true;
                target.FullName = source.Name;
            }            
            if (target.HomeAddress != source.Addredd)
            {
                dirty = true;
                target.HomeAddress = source.Addredd;
            }            
            return dirty;
        }
        
    }
}