use Enum.Parse<TEnum>

Author: lbargaoanu

src/AutoMapper/Mappers/EnumToEnumMapper.cs

@@ -14,14 +14,10 @@ public Expression MapExpression(IGlobalConfiguration configurationProvider, Prof
         {
             var destinationType = destExpression.Type;
             var sourceToString = Call(sourceExpression, ObjectToString);
-            var (tryParse, result) = TryParse(destinationType, sourceToString);
-            return Block(new[] { result }, Condition(tryParse, result, Convert(sourceExpression, destinationType)));
-        }
-        internal static (MethodCallExpression TryParse, ParameterExpression Result) TryParse(Type destinationType, Expression value)
-        {
             var result = Variable(destinationType, "destinationEnumValue");
             var ignoreCase = True;
-            return (Call(TryParseMethod.MakeGenericMethod(destinationType), value, ignoreCase, result), result);
+            var tryParse = Call(TryParseMethod.MakeGenericMethod(destinationType), sourceToString, ignoreCase, result);
+            return Block(new[] { result }, Condition(tryParse, result, Convert(sourceExpression, destinationType)));
         }
     }
 }

src/AutoMapper/Mappers/StringToEnumMapper.cs

@@ -9,7 +9,9 @@ namespace AutoMapper.Internal.Mappers
     using static Expression;
     public class StringToEnumMapper : IObjectMapper
     {
-        private static readonly MethodInfo EqualsMethod = typeof(StringToEnumMapper).GetMethod(nameof(StringCompareOrdinalIgnoreCase));
+        private static readonly MethodInfo EqualsMethod = typeof(StringToEnumMapper).GetMethod("StringCompareOrdinalIgnoreCase");
+        private static readonly MethodInfo ParseMethod = typeof(Enum).StaticGenericMethod("Parse", parametersCount: 2);
+        private static readonly PropertyInfo Length = typeof(string).GetProperty("Length");
         public bool IsMatch(TypePair context) => context.SourceType == typeof(string) && context.DestinationType.IsEnum;
         public Expression MapExpression(IGlobalConfiguration configurationProvider, ProfileMap profileMap,
             MemberMap memberMap, Expression sourceExpression, Expression destExpression)
@@ -27,9 +29,10 @@ public Expression MapExpression(IGlobalConfiguration configurationProvider, Prof
                     switchCases.Add(switchCase);
                 }
             }
-            var (tryParse, result) = EnumToEnumMapper.TryParse(destinationType, sourceExpression);
-            var returnValue = switchCases != null ? Switch(sourceExpression, result, EqualsMethod, switchCases) : (Expression)result;
-            return Block(new[] { result }, tryParse, returnValue);
+            var ignoreCase = True;
+            Expression enumParse = Call(ParseMethod.MakeGenericMethod(destinationType), sourceExpression, ignoreCase);
+            var parse = switchCases != null ? Switch(sourceExpression, enumParse, EqualsMethod, switchCases) : enumParse;
+            return Condition(Equal(Property(sourceExpression, Length), Zero), Default(destinationType), parse);
         }
         public static bool StringCompareOrdinalIgnoreCase(string x, string y) => StringComparer.OrdinalIgnoreCase.Equals(x, y);
     }

src/UnitTests/Enumerations.cs

@@ -6,6 +6,13 @@
 
 namespace AutoMapper.Tests
 {
+    public class InvalidStringToEnum : AutoMapperSpecBase
+    {
+        protected override MapperConfiguration CreateConfiguration() => new(_=> { });
+        [Fact]
+        public void Should_throw() => new Action(()=>Map<ConsoleColor>("d")).ShouldThrow<AutoMapperMappingException>().InnerException.Message.ShouldBe(
+            "Requested value 'd' was not found.");
+    }
     public class DefaultEnumValueToString : AutoMapperSpecBase
     {
         Destination _destination;