Get Authenticated User Id

GetUserInitializer.cs

using System;
using System.Web;
using Microsoft.ApplicationInsights.Channel;

public class GetUserInitializer :
    Microsoft.ApplicationInsights.Extensibility.ITelemetryInitializer
{
    public void Initialize(ITelemetry telemetry)
    {
        if (telemetry is Microsoft.ApplicationInsights.DataContracts.RequestTelemetry)
        {
            if (System.Web.HttpContext.Current.User.Identity.IsAuthenticated)
            {
                var telem = telemetry as Microsoft.ApplicationInsights.DataContracts.RequestTelemetry;
                var contextIdentity = System.Web.HttpContext.Current.User.Identity.Name;
                telem.Context.User.Id = contextIdentity;
            }
        }
    }
}