Display enums with string description in Swashbuckle/Swagger (ASP.NET Core 2)

EnumDocumentFilter.cs

/// <summary>
/// Add enum value descriptions to Swagger
/// </summary>
public class EnumDocumentFilter : IDocumentFilter
{
	/// <inheritdoc />
	public void Apply(SwaggerDocument swaggerDoc, DocumentFilterContext context)
	{
		foreach (var schemaDictionaryItem in swaggerDoc.Definitions)
		{
			var schema = schemaDictionaryItem.Value;
			foreach (var propertyDictionaryItem in schema.Properties)
			{
				var property = propertyDictionaryItem.Value;
				var propertyEnums = property.Enum;
				if (propertyEnums != null && propertyEnums.Count > 0)
				{
					property.Description += DescribeEnum(propertyEnums);
				}
			}
		}
		if (swaggerDoc.Paths.Count <= 0) return;

		// add enum descriptions to input parameters
		foreach (var pathItem in swaggerDoc.Paths.Values)
		{
			DescribeEnumParameters(pathItem.Parameters);

			// head, patch, options, delete left out
			var possibleParameterisedOperations = new List<Operation> { pathItem.Get, pathItem.Post, pathItem.Put };
			possibleParameterisedOperations.FindAll(x => x != null)
				.ForEach(x => DescribeEnumParameters(x.Parameters));
		}
	}
	private static void DescribeEnumParameters(IList<IParameter> parameters)
	{
		if (parameters == null) return;

		foreach (var param in parameters)
		{
			if (param is NonBodyParameter nbParam && nbParam.Enum?.Any() == true)
			{
				param.Description += DescribeEnum(nbParam.Enum);
			}
		}
	}

	private static string DescribeEnum(IEnumerable<object> enums)
	{
		var enumDescriptions = new List<string>();
		Type type = null;
		foreach (var enumOption in enums)
		{
			if (type == null)
			{
				type = enumOption.GetType();
			}
			var name = Enum.GetName(type, enumOption);
			if (!string.IsNullOrWhiteSpace(name))
			{
				var description = new StringBuilder(name);
				// process description
				for (var i = description.Length - 1; i > 0; i--)
				{
					if (i > 0 && char.IsUpper(description[i]))
					{
						description.Insert(i, ' ');
					}
				}

				enumDescriptions.Add($"{Convert.ChangeType(enumOption, type.GetEnumUnderlyingType())} = {description.ToString()}");
			}

		}

		return $"{Environment.NewLine}{string.Join(Environment.NewLine, enumDescriptions)}";
	}
}