EnumMember is not applied when enum value is a combination of flags.

[filzrev]

Describe the bug
When serialize enum value combinations.
value is serialized by default enum name.
And the name that is specified by EnumMember is not used.

To Reproduce

Test Code

[Flags]
public enum TestEnum
{
	[JsonStringEnumMemberName("A")]
	[EnumMember(Value = "A")]
	AAA = 1,
	[JsonStringEnumMemberName("B")]
	[EnumMember(Value = "B")]
	BBB = 2,
}

[Fact]
void YamlDotNetTest()
{
	var serializer = new SerializerBuilder().Build();

	// Arrange
	var value = TestEnum.AAA | TestEnum.BBB;

	// Act
	var result = serializer.Serialize(value);

	// Assert
	result.Should().Be("A, B\r\n"); // Failed. Expected: "A,B\r\n" but Actual: "AAA, BBB\r\n"
}

Serialize result of System.Text.Json / NewtonsoftJson

When serialize same value with System.Text.Json / NewtonsoftJson enum value is serialized as expected.

// System.Text.Json use `JsonStringEnumMemberName` attribute (EnumMember attribute is not used)
[Fact]
void SystemTextJsonTest()
{	
	var options = new JsonSerializerOptions { };
	options.Converters.Add(new JsonStringEnumConverter(JsonNamingPolicy.CamelCase));
	
	// Arrange
	var value = TestEnum.AAA | TestEnum.BBB;

	// Act
	var result = System.Text.Json.JsonSerializer.Serialize(value, options);

	// Assert
	result.Should().Be("\"A, B\""); // Success
}

// NewtonsoftJson use `EnumMember` attribute.
[Fact]
void NewtonsoftJsonTest()
{
	// Arrange
	var value = TestEnum.AAA | TestEnum.BBB;

	// Act
	var result = JsonConvert.SerializeObject(value, new Newtonsoft.Json.Converters.StringEnumConverter());

	// Assert
	result.Should().Be("\"A, B\""); // Success
}

[EdwardCooke]

We do support enum member but only in .net core. Full framework doesn’t have that functionality. Are you doing this in a .net core 6/7/8 app or full framework 4.x?

[filzrev]

I'm using .NET 8 or later.
So there is no need for .NET Framework supports on my usecase.

By the way, is there any reasons that exclude EnumMember support for .NET Framework 4.x?

It's explicitly excluded by #ifdef preprocessors.
But these code seems it can successfully build when targeting .NET Framework 4.7 or later. (It support .NET Standard 2.0)

YamlDotNet/YamlDotNet/Serialization/TypeInspectors/ReflectionTypeInspector.cs

Lines 34 to 69 in 7bed5cf

	public override string GetEnumName(Type enumType, string name)
	{
	#if NETSTANDARD2_0_OR_GREATER || NET6_0_OR_GREATER
	foreach (var enumMember in enumType.GetMembers())
	{
	var attribute = enumMember.GetCustomAttribute<EnumMemberAttribute>();
	if (attribute?.Value == name)
	{
	return enumMember.Name;
	}
	}
	#endif
	return name;
	}
	public override string GetEnumValue(object enumValue)
	{
	if (enumValue == null)
	{
	return string.Empty;
	}
	var result = enumValue.ToString();
	#if NETSTANDARD2_0_OR_GREATER || NET6_0_OR_GREATER
	var type = enumValue.GetType();
	var enumMembers = type.GetMember(result);
	if (enumMembers.Length > 0)
	{
	var attribute = enumMembers[0].GetCustomAttribute<EnumMemberAttribute>();
	if (attribute?.Value != null)
	{
	result = attribute.Value;
	}
	}
	#endif
	return result!;
	}