Support for conditionally mapping complex type properties to null when overwriting

Author: SteveWilkes

AgileMapper.UnitTests/Configuration/WhenMappingToNull.cs

@@ -1,5 +1,6 @@
 namespace AgileObjects.AgileMapper.UnitTests.Configuration
 {
+    using System;
     using Shouldly;
     using TestClasses;
     using Xunit;
@@ -54,5 +55,41 @@ public void ShouldRestrictAConfiguredMapToNullConditionBySourceType()
                 matchingResult.Address.ShouldBeNull();
             }
         }
+
+        [Fact]
+        public void ShouldOverwriteAPropertyToNull()
+        {
+            using (var mapper = Mapper.CreateNew())
+            {
+                mapper.WhenMapping
+                    .Over<Address>()
+                    .If(ctx => ctx.Target.Line1 == null)
+                    .MapToNull();
+
+                var nonMatchingSource = new CustomerViewModel
+                {
+                    Id = Guid.NewGuid(),
+                    AddressLine1 = "Places!"
+                };
+                var target = new Customer { Address = new Address { Line1 = "Home!" } };
+
+                mapper.Map(nonMatchingSource).Over(target);
+
+                target.Address.ShouldNotBeNull();
+                target.Address.Line1.ShouldBe("Places!");
+
+                var matchingSource = new CustomerViewModel { Id = Guid.NewGuid() };
+
+                mapper.Map(matchingSource).Over(target);
+
+                target.Address.ShouldBeNull();
+
+                var nullAddressTarget = new Customer();
+
+                mapper.Map(matchingSource).Over(nullAddressTarget);
+
+                target.Address.ShouldBeNull();
+            }
+        }
     }
 }

AgileMapper/Configuration/MapToNullCondition.cs

@@ -1,10 +1,22 @@
 namespace AgileObjects.AgileMapper.Configuration
 {
+    using System.Linq.Expressions;
+    using Members;
+    using ObjectPopulation;
+
     internal class MapToNullCondition : UserConfiguredItemBase
     {
         public MapToNullCondition(MappingConfigInfo configInfo)
             : base(configInfo)
         {
         }
+
+        protected override Expression GetConditionOrNull(IMemberMapperData mapperData, CallbackPosition position)
+        {
+            mapperData.Context.UsesMappingDataObjectAsParameter =
+                ConfigInfo.ConditionUsesMappingDataObjectParameter;
+
+            return base.GetConditionOrNull(mapperData, position);
+        }
     }
 }