SelectListFactory examples for blog

ISelectable.cs

    public interface ISelectable
    {
        string GetValueField();
        string GetTextField();
    }

NewSelectListfactory.cs

    public class SelectListFactory : ISelectListFactory
    {
        public SelectList Create<T>(IEnumerable<T> listOfT) where T : ISelectable
        {
            var selectListItems = listOfT.Select(arg => new SelectListItem
            {
                Text = arg.GetTextField(),
                Value = arg.GetValueField()
            });

            return new SelectList(selectListItems.ToList(), "Value", "Text");
        }
    }

NewSelectListFactoryTests.cs

    internal class SelectListFactoryTests
    {
        [TestFixture]
        public class when_creating_a_select_List_factory_with_funcs
        {

            public class TestSelectable : ISelectable
            {
                public string GetValueField()
                {
                    return "Value";
                }

                public string GetTextField()
                {
                    return "Test";
                }
            }

            [Test]
            public void then_should_use_text_field_of_test_selectable()
            {
                // Arrange
                var factory = new SelectListFactory();

                // Act
                var selectList = factory.Create(new List<TestSelectable> {new TestSelectable()});

                // Assert
                Assert.That(selectList.All(item => item.Text == "Test"), Is.True);
            }

            [Test]
            public void then_should_use_value_field_of_test_selectable()
            {
                // Arrange
                var factory = new SelectListFactory();

                // Act
                var selectList = factory.Create(new List<TestSelectable> {new TestSelectable()});

                // Assert
                Assert.That(selectList.All(item => item.Value == "Value"), Is.True);
            }

            [Test]
            public void then_should_throw_exception_given_null_list_of_items()
            {
                // Arrange
                var factory = new SelectListFactory();

                // Act // Assert
                Assert.Throws<ArgumentNullException>(() => factory.Create((List<TestSelectable>) null));
            }
        }
    }

OldSelectListFactory.cs

    public class SelectListFactory : ISelectListFactory
    {
        public SelectList CreateSelectList<T>(IEnumerable<T> items, string dataValueProperty, string dataTextProperty)
        {
            return new SelectList(items, dataValueProperty, dataTextProperty);
        }

        public SelectList CreateSelectList<T>(IEnumerable<T> items, Func<T, object> valueExpression, Func<T, object> textExpression)
        {
            return CreateSelectList(items, valueExpression, textExpression, null);
        }

        public SelectList CreateSelectList<T>(IEnumerable<T> items, Func<T, object> valueExpression,
            Func<T, object> textExpression, object selectedValue)
        {
            
            var enumerable = items.Select(item => new SelectListItem
            {
                Text = textExpression.Invoke(item).ToString(),
                Value = valueExpression.Invoke(item).ToString(),
            });

            return new SelectList(enumerable.ToList(), "Value", "Text", selectedValue);
        }
    }