DateTimes that are exported in ISO8601 are not consistent across serialization formats JSON/XML/CSV (#507)

* CSV DateTime formatting for midnight fix

DateTimes that are exported in ISO8601 are not consistent across serialization for midnight on days.

JSON and XML both show a datetime with the fractional seconds like so

`2018-02-10T00:00:00.0000000Z`

but CSV will produce a DateTime with out the any of the timespan portion of timezone indicator i.e.

`2018-01-01`

this is also not consistent with the default ISO8601 parser in .NET for DateTime called as so `.ToString("o")` will produce the ISO8601 serialized times as for JSON and XML, but not CSV.

Adding the ability to specify a DateTimeFormat that will allow a user to override the DateTimeFormat defaults so serialized value is consistent

* Remove unused System.Globalization reference

Author: Siliconrob

src/ServiceStack.Text/Common/DateTimeSerializer.cs

@@ -443,8 +443,12 @@ public static TimeSpan ParseXsdTimeSpan(string dateTimeStr)
         public static string ToShortestXsdDateTimeString(DateTime dateTime)
         {
             dateTime = dateTime.UseConfigSpecifiedSetting();
-            var timeOfDay = dateTime.TimeOfDay;
+            if (!string.IsNullOrEmpty(JsConfig.DateTimeFormat))
+            {
+                return dateTime.ToString(JsConfig.DateTimeFormat, CultureInfo.InvariantCulture);
+            }
 
+            var timeOfDay = dateTime.TimeOfDay;
             var isStartOfDay = timeOfDay.Ticks == 0;
             if (isStartOfDay && !JsConfig.SkipDateTimeConversion)
                 return dateTime.ToString(ShortDateTimeFormat, CultureInfo.InvariantCulture);

src/ServiceStack.Text/JsConfig.cs

@@ -222,6 +222,7 @@ public static JsConfigScope With(
             bool? preferInterfaces = null,
             bool? throwOnDeserializationError = null,
             string typeAttr = null,
+            string dateTimeFormat = null,
             Func<Type, string> typeWriter = null,
             Func<string, Type> typeFinder = null,
             bool? treatEnumAsInteger = null,
@@ -258,6 +259,7 @@ public static JsConfigScope With(
                 PropertyConvention = propertyConvention ?? sPropertyConvention,
                 PreferInterfaces = preferInterfaces ?? sPreferInterfaces,
                 ThrowOnDeserializationError = throwOnDeserializationError ?? sThrowOnDeserializationError,
+                DateTimeFormat = dateTimeFormat ?? sDateTimeFormat,
                 TypeAttr = typeAttr ?? sTypeAttr,
                 TypeWriter = typeWriter ?? sTypeWriter,
                 TypeFinder = typeFinder ?? sTypeFinder,
@@ -274,6 +276,21 @@ public static JsConfigScope With(
             };
         }
 
+        private static string sDateTimeFormat;
+        public static string DateTimeFormat
+        {
+            get
+            {
+                return (JsConfigScope.Current != null ? JsConfigScope.Current.DateTimeFormat : null)
+                       ?? sDateTimeFormat;
+                       //?? DateTimeSerializer.XsdDateTimeFormatSeconds;
+            }
+            set
+            {
+                if (sDateTimeFormat == null) sDateTimeFormat = value;
+            }
+        }
+
         private static bool? sConvertObjectTypesIntoStringDictionary;
         public static bool ConvertObjectTypesIntoStringDictionary
         {
@@ -974,6 +991,7 @@ public static void Reset()
             sPreferInterfaces = null;
             sThrowOnDeserializationError = null;
             sTypeAttr = null;
+            sDateTimeFormat = null;
             sJsonTypeAttrInObject = null;
             sJsvTypeAttrInObject = null;
             sTypeWriter = null;

src/ServiceStack.Text/JsConfigScope.cs

@@ -61,6 +61,7 @@ public void Dispose()
         public bool? ExcludeTypeInfo { get; set; }
         public bool? IncludeTypeInfo { get; set; }
         public string TypeAttr { get; set; }
+        public string DateTimeFormat { get; set; }
         internal string JsonTypeAttrInObject { get; set; }
         internal string JsvTypeAttrInObject { get; set; }
         public Func<Type, string> TypeWriter { get; set; }

tests/ServiceStack.Text.Tests/CsvTests/ObjectSerializerTests.cs

@@ -8,6 +8,56 @@ namespace ServiceStack.Text.Tests.CsvTests
     [TestFixture]
     public class ObjectSerializerTests
     {
+        [Test]
+        public void MidnightAndNoonTestSerialization()
+        {
+            JsConfig.Reset();
+            JsConfig<DateTime>.SerializeFn = null;
+            JsConfig<DateTime>.Reset();
+
+            JsConfig.AlwaysUseUtc = true;
+            JsConfig.AssumeUtc = true;
+            // Set the format for DatTimeFormatting explicitly using DateTimeSerializer.XsdDateTimeFormat because it is ISO8601 fractional seconds
+            JsConfig.DateTimeFormat = DateTimeSerializer.XsdDateTimeFormat;
+
+            var midnight = new DateTime(2018, 1, 1, 0, 0, 0, DateTimeKind.Utc);
+            var noon = midnight.AddHours(12);
+            var dotnetValues = new
+            {
+                Midnight = midnight.ToString("o"),
+                Noon = noon.ToString("o")
+            };
+            var data = new object[] {
+                    new POCO { DateTime = midnight },
+                    new POCO { DateTime = noon }
+                    };
+            var csv = CsvSerializer.SerializeToCsv(data);
+            // Reset back to defaults
+            JsConfig.Reset();
+            JsConfig<DateTime>.SerializeFn = null;
+            JsConfig<DateTime>.Reset();
+
+            Console.WriteLine(csv);
+
+            const string endLineChars = "\r\n";
+            Assert.AreEqual($"DateTime{endLineChars}" +
+                            $"{dotnetValues.Midnight}{endLineChars}" +
+                            $"{dotnetValues.Noon}{endLineChars}", csv);
+
+            // Now don't use custom DateTimeFormat
+            JsConfig.AlwaysUseUtc = true;
+            JsConfig.AssumeUtc = true;            
+            csv = CsvSerializer.SerializeToCsv(data);
+            Console.WriteLine(csv);
+            Assert.AreEqual($"DateTime{endLineChars}" +
+                            $"2018-01-01{endLineChars}" +
+                            $"2018-01-01T12:00:00Z{endLineChars}", csv);
+
+            JsConfig.Reset();
+            JsConfig<DateTime>.SerializeFn = null;
+            JsConfig<DateTime>.Reset();
+        }
+
         [Test]
         public void IEnumerableObjectSerialization()
         {