Swagger UI - Add required header

One of our REST API’s always requires an ‘X-API-Key’ header. To simplify testing, I wanted to have the option to specify the header in the Swagger UI.

Let’s see how we can get this done through SwashBuckle.

First I need to create a custom IOperationFilter that will add the header:

	using System;
	using System.Collections.Generic;
	using System.Linq;
	using System.Threading.Tasks;
	using Microsoft.OpenApi.Models;
	using Swashbuckle.AspNetCore.SwaggerGen;
	public class AddHeaderParameter : IOperationFilter
	{
	public void Apply(OpenApiOperation operation, OperationFilterContext context)
	{
	if (operation.Parameters == null)
	operation.Parameters = new List<OpenApiParameter>();
	operation.Parameters.Add(new OpenApiParameter
	{
	Name = "X-Api-Key",
	In = ParameterLocation.Header,
	Required = true,
	Schema = new OpenApiSchema
	{
	Type = "string"
	}
	});
	}
	}

view raw AddHeaderParameter.cs hosted with ❤ by GitHub

Now we need to update our Swagger configuration to use this header:

	// Register the Swagger generator, defining 1 or more Swagger documents
	services.AddSwaggerGen(c =>
	{
	c.SwaggerDoc("v1", new OpenApiInfo { Title = "Example API", Version = "v1" });
	c.OperationFilter<AddHeaderParameter>();
	});

view raw AddSwaggerGen.cs hosted with ❤ by GitHub

If we now run our application and browse to the Swagger UI, we should see the extra header parameter: