From 1febb9a211680b22da10c07973e1b44502ab86f4 Mon Sep 17 00:00:00 2001
From: Sipke Schoorstra <sipkeschoorstra@outlook.com>
Date: Wed, 5 May 2021 13:13:05 +0200
Subject: [PATCH] Handle DateTime parsing for UTC strings

---
 src/core/Elsa.Core/Expressions/LiteralHandler.cs | 15 +++------------
 .../Elsa.Core/Extensions/StringExtensions.cs     | 16 ++++++++++++----
 .../Expressions/LiteralHandlerTests.cs           |  3 ++-
 3 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/src/core/Elsa.Core/Expressions/LiteralHandler.cs b/src/core/Elsa.Core/Expressions/LiteralHandler.cs
index a4520deea..9b52aa202 100644
--- a/src/core/Elsa.Core/Expressions/LiteralHandler.cs
+++ b/src/core/Elsa.Core/Expressions/LiteralHandler.cs
@@ -1,5 +1,6 @@
 using System;
 using System.ComponentModel;
+using System.Globalization;
 using System.Threading;
 using System.Threading.Tasks;
 using Elsa.Services.Models;
@@ -14,17 +15,7 @@ namespace Elsa.Expressions
             string expression,
             Type returnType,
             ActivityExecutionContext context,
-            CancellationToken cancellationToken)
-        {
-            if (returnType == typeof(string) || returnType == typeof(object))
-                return Task.FromResult<object?>(expression);
-
-            if (string.IsNullOrWhiteSpace(expression))
-                return Task.FromResult((object?) null);
-            
-            var converter = TypeDescriptor.GetConverter(returnType);
-            var value = converter.CanConvertFrom(typeof(string)) ? converter.ConvertFrom(expression) : default;
-            return Task.FromResult(value)!;
-        }
+            CancellationToken cancellationToken) =>
+            Task.FromResult(expression.Parse(returnType));
     }
 }
\ No newline at end of file
diff --git a/src/core/Elsa.Core/Extensions/StringExtensions.cs b/src/core/Elsa.Core/Extensions/StringExtensions.cs
index 65563bd2e..e86da59ec 100644
--- a/src/core/Elsa.Core/Extensions/StringExtensions.cs
+++ b/src/core/Elsa.Core/Extensions/StringExtensions.cs
@@ -1,19 +1,27 @@
 using System;
 using System.ComponentModel;
+using System.Globalization;
 
 namespace Elsa
 {
     public static class StringExtensions
     {
-        public static T Parse<T>(this string value) => (T)value.Parse(typeof(T));
+        public static T? Parse<T>(this string value) => (T?)value.Parse(typeof(T));
 
-        public static object Parse(this string value, Type targetType)
+        public static object? Parse(this string value, Type targetType)
         {
-            if (typeof(string) == targetType || typeof(object) == targetType || targetType == default)
+            if (typeof(string) == targetType || typeof(object) == targetType || targetType == default!)
                 return value;
             
+            // Handling DateTime explicitly due to an issue with converting UTC strings to DateTime as outlined here: https://stackoverflow.com/questions/11130912/datetimeconverter-converting-from-utc-string
+            if(targetType == typeof(DateTime))
+                return DateTime.Parse(value, null, DateTimeStyles.RoundtripKind);
+            
+            if (string.IsNullOrWhiteSpace(value))
+                return null!;
+            
             var converter = TypeDescriptor.GetConverter(targetType);
-            return converter.ConvertFromString(value)!;
+            return converter.CanConvertFrom(typeof(string)) ? converter.ConvertFrom(value) : default;
         }
     }
 }
\ No newline at end of file
diff --git a/test/unit/Elsa.UnitTests/Expressions/LiteralHandlerTests.cs b/test/unit/Elsa.UnitTests/Expressions/LiteralHandlerTests.cs
index bc2e7e341..415c6837c 100644
--- a/test/unit/Elsa.UnitTests/Expressions/LiteralHandlerTests.cs
+++ b/test/unit/Elsa.UnitTests/Expressions/LiteralHandlerTests.cs
@@ -57,7 +57,8 @@ namespace Elsa.Expressions
                                                                                           [StubActivityExecutionContext] ActivityExecutionContext context)
         {
             var result = await sut.EvaluateAsync("2001-03-04T12:45:32Z", typeof(DateTime), context, default);
-            Assert.Equal(new DateTime(2001, 03, 04, 12, 45, 32, DateTimeKind.Utc), result);
+            var expected = new DateTime(2001, 03, 04, 12, 45, 32, DateTimeKind.Utc);
+            Assert.Equal(expected, result);
         }
     }
 }
\ No newline at end of file