TrackRequestBodyAttribute.cs

using System.IO;
using System.Text;
using System.Threading.Tasks;
using Microsoft.ApplicationInsights;
using Microsoft.ApplicationInsights.DataContracts;
using Microsoft.AspNetCore.Mvc.Filters;

namespace YourNamespace
{
	public class TrackConstants
	{
		public const string JsonBody = "JsonBody";
	}
	
	public class TrackRequestBodyAttribute : ActionFilterAttribute
	{
		private readonly TelemetryClient _telemtry;

		public TrackRequestBodyAttribute(
			TelemetryClient telemetry = null
		)
		{
			_telemtry = telemetry;
		}

		public override async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
		{
			var request = context.HttpContext.Request;
			
			request.Body.Position = 0;
			using var stream = new StreamReader(request.Body, Encoding.UTF8, false, 1024, true);
			var body = await stream.ReadToEndAsync();
			request.Body.Position = 0;
			context.HttpContext.Items.Add(TrackConstants.JsonBody, body);

			var toperation = _telemtry.StartNewOperation<DependencyTelemetry>("JsonBody");
			toperation.TData.Add(TrackConstants.JsonBody, body);
			toperation.Stop();

			await base.OnActionExecutionAsync(context, next);
		}
	}
}