Web Api How to add a Header parameter for all API in Swagger

What the user "G T" wrote is correct but it is not working with Swagger 5. We have some new changes:

From: Operation to: OpenApiOperation

From: IParameter to: OpenApiParameter

From: NonBodyParameter to: OpenApiParameter, and the most important is...

From: Type = "string" to: Schema = new OpenApiSchema { Type = "String" }

using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNetCore.Mvc.Authorization;
using Microsoft.OpenApi.Any;
using Microsoft.OpenApi.Models;
using Swashbuckle.AspNetCore.SwaggerGen;
namespace MyAPI
{
    public class AuthorizationHeaderParameterOperationFilter: IOperationFilter
    {
        public void Apply(OpenApiOperation operation, OperationFilterContext context)
        {
            var filterPipeline = context.ApiDescription.ActionDescriptor.FilterDescriptors;
            var isAuthorized = filterPipeline.Select(filterInfo => filterInfo.Filter).Any(filter => filter is AuthorizeFilter);
            var allowAnonymous = filterPipeline.Select(filterInfo => filterInfo.Filter).Any(filter => filter is IAllowAnonymousFilter);

            if (isAuthorized && !allowAnonymous)
            {
                if (operation.Parameters == null)
                    operation.Parameters = new List<OpenApiParameter>();

                operation.Parameters.Add(new OpenApiParameter 
                {
                    Name = "Authorization",
                    In = ParameterLocation.Header,
                    Description = "access token",
                    Required = true,
                    Schema = new OpenApiSchema
                    {
                        Type = "string",
                        Default = new OpenApiString("Bearer ")
                    }
                });
            }
        }
    }
}

And in Startup => ConfigureServices => services.AddSwaggerGen()

c.OperationFilter<AuthorizationHeaderParameterOperationFilter>();

Yes you can do it via inheriting from IOperationFilter

You can find the answer on GitHub here: AddRequiredHeaderParameter

using System.Collections.Generic;
using Microsoft.AspNetCore.Mvc.ApiExplorer;
using Swashbuckle.AspNetCore.Swagger;
using Swashbuckle.AspNetCore.SwaggerGen;

public class AddRequiredHeaderParameter : IOperationFilter
{
    public void Apply(Operation operation, OperationFilterContext context)
    {
        if (operation.Parameters == null)
            operation.Parameters = new List<IParameter>();

        operation.Parameters.Add(new NonBodyParameter
            {
                Name = "X-User-Token",
                In = "header",
                Type = "string",
                Required = false
            });
    }
}

Then you go to your SwaggerConfig.cs file and add the following in the AddSwaggerGen section:

c.OperationFilter<AddRequiredHeaderParameter>();

Rebuild, and enjoy.