StackOverFlowAnswers.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Expressions;
using AutoMapper;
using NUnit.Framework;

namespace StackOverFlowAnswers
{
    #region http://stackoverflow.com/questions/16558005/how-can-i-set-default-value-to-exceptions-in-automapper-while-mapping-from-strin/16558388#16558388

    public class LineItem
    {
        public int Id { get; set; }
        public string ProductId { get; set; }
        public int Amount { get; set; }
    }

    public class Model
    {
        public int Id { get; set; }
        public string ProductId { get; set; }
        public string Amount { get; set; }
    }

    
    public class AutoMappingTests
    {

        public static void Do(int value, Action<int> action)
        {
            for (int i = 0; i < value; i++)
            {
                action(i);
            }
        }

        [TestFixtureSetUp]
        public void TestFixtureSetUp()
        {
            Mapper.CreateMap<Model, LineItem>()
                .ForMember(x => x.Amount, opt => opt.ResolveUsing<StringToInteger>());
        }

        [Test]
        public void TestBadStringToDefaultInteger()
        {
            // Arrange
            var model = new Model() {Id = 1, ProductId = "awesome-product-133-XP", Amount = "EVIL STRING, MWUAHAHAHAH"};

            // Act
            LineItem mapping1 = Mapper.Map<LineItem>(model);

            // Assert
            Assert.AreEqual(model.Id, mapping1.Id);
            Assert.AreEqual(model.ProductId, mapping1.ProductId);
            Assert.AreEqual(0, mapping1.Amount);


            // Arrange
            model.Amount = null; // now we test null, which we said in options to map from null to -1

            // Act
            LineItem mapping2 = Mapper.Map<LineItem>(model);

            // Assert
            Assert.AreEqual(-1, mapping2.Amount);

        }
    }

    public class StringToInteger : ValueResolver<Model, int>
    {
        protected override int ResolveCore(Model source)
        {
            if (source.Amount == null)
            {
                return -1;
            }

            int value;

            if (int.TryParse(source.Amount, out value))
            {
                return value; // Wahayy!!
            }

            return 0; // return 0 if it could not parse!
        }
    }

    #endregion

}