btcpayserver/BTCPayServer/Filters/XFrameOptionsAttribute.cs

using Microsoft.AspNetCore.Mvc.Filters;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;

namespace BTCPayServer.Filters
{
	public class XFrameOptionsAttribute : Attribute, IActionFilter
	{
		public XFrameOptionsAttribute(string value)
		{
			Value = value;
		}
		public string Value
		{
			get; set;
		}
		public void OnActionExecuted(ActionExecutedContext context)
		{
			
		}

		public void OnActionExecuting(ActionExecutingContext context)
		{
			var existing = context.HttpContext.Response.Headers["x-frame-options"].FirstOrDefault();
			if(existing != null && Value == null)
				context.HttpContext.Response.Headers.Remove("x-frame-options");
			else
				context.HttpContext.Response.Headers["x-frame-options"] = Value;
		}
	}
}