Support for configuring specific-value-type dictionary mapping

Author: SteveWilkes

AgileMapper.UnitTests/Configuration/WhenConfiguringDictionaryMapping.cs

@@ -391,5 +391,35 @@ public void ShouldConditionallyMapToDerivedTypes()
                 ((MysteryCustomerViewModel)mysteryCustomerResult).Report.ShouldBe("Very good!");
             }
         }
+
+        [Fact]
+        public void ShouldConditionallyMapToDerivedTypesFromASpecificValueTypeDictionary()
+        {
+            using (var mapper = Mapper.CreateNew())
+            {
+                mapper.WhenMapping
+                    .FromDictionariesWithValueType<string>()
+                    .ToANew<CustomerViewModel>()
+                    .If(s => s.Source["Report"].Length > 10)
+                    .MapTo<MysteryCustomerViewModel>();
+
+                var source = new Dictionary<string, string>
+                {
+                    ["Name"] = "Customer",
+                    ["Report"] = "Too short!"
+                };
+                var customerResult = mapper.Map(source).ToANew<CustomerViewModel>();
+
+                customerResult.ShouldBeOfType<CustomerViewModel>();
+                customerResult.Name.ShouldBe("Customer");
+
+                source["Report"] = "Plenty long enough!";
+                var mysteryCustomerResult = mapper.Map(source).ToANew<CustomerViewModel>();
+
+                mysteryCustomerResult.ShouldBeOfType<MysteryCustomerViewModel>();
+                mysteryCustomerResult.Name.ShouldBe("Customer");
+                ((MysteryCustomerViewModel)mysteryCustomerResult).Report.ShouldBe("Plenty long enough!");
+            }
+        }
     }
 }

AgileMapper/Api/Configuration/MappingConfigStartingPoint.cs

@@ -261,10 +261,19 @@ public InstanceConfigurator<TObject> InstancesOf<TObject>() where TObject : clas
         /// <summary>
         /// Configure how this mapper performs mappings from source Dictionary{string, T} instances.
         /// </summary>
-        /// <returns>A DictionaryConfigurator with which to continue the configuration.</returns>
         public DictionaryConfigurator<object> FromDictionaries
             => new DictionaryConfigurator<object>(MappingConfigInfo.AllSourceTypes(_mapperContext));
 
+        /// <summary>
+        /// Configure how this mapper performs mappings from source Dictionary{string, TValue} instances.
+        /// </summary>
+        /// <typeparam name="TValue">
+        /// The type of values contained in the Dictionary to which the configuration will apply.
+        /// </typeparam>
+        /// <returns>A DictionaryConfigurator with which to continue the configuration.</returns>
+        public DictionaryConfigurator<TValue> FromDictionariesWithValueType<TValue>()
+            => new DictionaryConfigurator<TValue>(MappingConfigInfo.AllSourceTypes(_mapperContext));
+
         /// <summary>
         /// Configure how this mapper performs mappings from the source type specified by the given 
         /// <paramref name="exampleInstance"/>. Use this overload for anonymous types.