Swagger C# Enum generation

So these are the two Enum Helpers I'm using. One is used by NSwag (x-enumNames) and the other is used by Azure AutoRest (x-ms-enums)

Finally found the reference for EnumDocumentFilter (https://stackoverflow.com/a/49941775/1910735)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using Swashbuckle.AspNetCore.Swagger;
using Swashbuckle.AspNetCore.SwaggerGen;

namespace SwaggerDocsHelpers
{
    /// <summary>
    /// Add enum value descriptions to Swagger
    /// https://stackoverflow.com/a/49941775/1910735
    /// </summary>
    public class EnumDocumentFilter : IDocumentFilter
    {
        /// <inheritdoc />
        public void Apply(SwaggerDocument swaggerDoc, DocumentFilterContext context)
        {
            // add enum descriptions to result models
            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);
                }
                else if (param.Extensions.ContainsKey("enum") && param.Extensions["enum"] is IList<object> paramEnums &&
                  paramEnums.Count > 0)
                {
                    param.Description += DescribeEnum(paramEnums);
                }
            }
        }

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

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

    public class EnumFilter : ISchemaFilter
    {
        public void Apply(Schema model, SchemaFilterContext context)
        {
            if (model == null)
                throw new ArgumentNullException("model");

            if (context == null)
                throw new ArgumentNullException("context");


            if (context.SystemType.IsEnum)
            {

                var enumUnderlyingType = context.SystemType.GetEnumUnderlyingType();
                model.Extensions.Add("x-ms-enum", new
                {
                    name = context.SystemType.Name,
                    modelAsString = false,
                    values = context.SystemType
                    .GetEnumValues()
                    .Cast<object>()
                    .Distinct()
                    .Select(value =>
                    {
                        //var t = context.SystemType;
                        //var convereted = Convert.ChangeType(value, enumUnderlyingType);
                        //return new { value = convereted, name = value.ToString() };
                        return new { value = value, name = value.ToString() };
                    })
                    .ToArray()
                });
            }
        }
    }


    /// <summary>
    /// Adds extra schema details for an enum in the swagger.json i.e. x-enumNames (used by NSwag to generate Enums for C# client)
    /// https://github.com/RicoSuter/NSwag/issues/1234
    /// </summary>
    public class NSwagEnumExtensionSchemaFilter : ISchemaFilter
    {
        public void Apply(Schema model, SchemaFilterContext context)
        {
            if (model == null)
                throw new ArgumentNullException("model");

            if (context == null)
                throw new ArgumentNullException("context");


            if (context.SystemType.IsEnum)
            {
                var names = Enum.GetNames(context.SystemType);
                model.Extensions.Add("x-enumNames", names);
            }
        }
    }
}

Then in your startup.cs you configure them

        services.AddSwaggerGen(c =>
        {
            ... the rest of your configuration

            // REMOVE THIS to use Integers for Enums
            // c.DescribeAllEnumsAsStrings();

            // add enum generators based on whichever code generators you decide
            c.SchemaFilter<NSwagEnumExtensionSchemaFilter>();
            c.SchemaFilter<EnumFilter>();
        });

This should generate your enums as this in the Swagger.json file

        sensorType: {
          format: "int32",
          enum: [
            0,
            1,
            2,
            3
          ],
          type: "integer",
          x-enumNames: [
            "NotSpecified",
            "Temperature",
            "Fuel",
            "Axle"
          ],
          x-ms-enum: {
            name: "SensorTypesEnum",
            modelAsString: false,
            values: [{
                value: 0,
                name: "NotSpecified"
              },
              {
                value: 1,
                name: "Temperature"
              },
              {
                value: 2,
                name: "Fuel"
              },
              {
                value: 3,
                name: "Axle"
              }
            ]
          }
        },

There is one issue with this solution though, (which I haven't had time to look into) Is that the Enum names are generated with my DTO names in NSwag - If you do find a solution to this do let me know :-)

Example, the following Enum was generated using NSwag: