IOperationFilter for OpenAPI models to support OData parameters

ODataOperationFilter.cs

using Microsoft.AspNetCore.Authorization;
using Microsoft.AspNetCore.Mvc.Controllers;
using Microsoft.OpenApi.Models;
using Swashbuckle.AspNetCore.SwaggerGen;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace MySolution
{
    public class ODataOperationFilter : IOperationFilter
    {
        public void Apply(OpenApiOperation operation, OperationFilterContext context)
        {
            if (operation.Parameters == null) operation.Parameters = new List<OpenApiParameter>();

            var descriptor = context.ApiDescription.ActionDescriptor as ControllerActionDescriptor;

            if (descriptor != null && descriptor.FilterDescriptors.Any(filter => filter.Filter is Microsoft.AspNetCore.OData.Query.EnableQueryAttribute))
            {
                operation.Parameters.Add(new OpenApiParameter()
                {
                    Name = "$select",
                    In = ParameterLocation.Query,
                    Schema = new OpenApiSchema
                    {
                        Type = "string",
                    },
                    Description = "Returns only the selected properties. (ex. FirstName, LastName, City)",
                    Required = false
                });

                operation.Parameters.Add(new OpenApiParameter()
                {
                    Name = "$expand",
                    In = ParameterLocation.Query,
                    Schema = new OpenApiSchema
                    {
                        Type = "string",
                    },
                    Description = "Include only the selected objects. (ex. Childrens, Locations)",
                    Required = false
                });

                operation.Parameters.Add(new OpenApiParameter()
                {
                    Name = "$filter",
                    In = ParameterLocation.Query,
                    Schema = new OpenApiSchema
                    {
                        Type = "string",
                    },
                    Description = "Filter the response with OData filter queries.",
                    Required = false
                });

                operation.Parameters.Add(new OpenApiParameter()
                {
                    Name = "$top",
                    In = ParameterLocation.Query,
                    Schema = new OpenApiSchema
                    {
                        Type = "string",
                    },
                    Description = "Number of objects to return. (ex. 25)",
                    Required = false
                });

                operation.Parameters.Add(new OpenApiParameter()
                {
                    Name = "$skip",
                    In = ParameterLocation.Query,
                    Schema = new OpenApiSchema
                    {
                        Type = "string",
                    },
                    Description = "Number of objects to skip in the current order (ex. 50)",
                    Required = false
                });

                operation.Parameters.Add(new OpenApiParameter()
                {
                    Name = "$orderby",
                    In = ParameterLocation.Query,
                    Schema = new OpenApiSchema
                    {
                        Type = "string",
                    },
                    Description = "Define the order by one or more fields (ex. LastModified)",
                    Required = false
                });

            }
        }
    }
}

Very useful, thank you. Is there a way to not show $expand in Swagger, if it's not allowed?

No $expand in OData setup:

builder.Services
    .AddControllers()
    .AddOData(options => options.Select().Filter().OrderBy().SetMaxTop(50));

@rgudkov-uss then remove the block starting at linie 34 and ending at 44. But it is for all operations.

@jacobmohl this would exclude $expand for all endpoints. Instead, I did a modification of your code to only show allowed odata parameters. Check it out: https://gist.github.com/rgudkov-uss/564a7faf92d90b7f2257b10000ac2515

@rgudkov-uss that’s great. 🙌👌🏻 I didn’t researched that much. Thanks