Umbraco-CMS/src/Umbraco.Core/SystemUtilities.cs

using System.Security;
using System.Web;

namespace Umbraco.Core
{
    /// <summary>
    /// Static helper methods for returning information about the current System
    /// </summary>
    public static class SystemUtilities
    {
        private static bool _knowTrustLevel;
        private static AspNetHostingPermissionLevel _trustLevel;

        /// <summary>
        /// Get the current trust level of the hosted application
        /// </summary>
        /// <returns></returns>
        public static AspNetHostingPermissionLevel GetCurrentTrustLevel()
        {
            if (_knowTrustLevel) return _trustLevel;

            foreach (var trustLevel in new[] {
                                                 AspNetHostingPermissionLevel.Unrestricted,
                                                 AspNetHostingPermissionLevel.High,
                                                 AspNetHostingPermissionLevel.Medium,
                                                 AspNetHostingPermissionLevel.Low,
                                                 AspNetHostingPermissionLevel.Minimal })
            {
                try
                {
                    new AspNetHostingPermission(trustLevel).Demand();
                }
                catch (SecurityException)
                {
                    continue;
                }

                _trustLevel = trustLevel;
                _knowTrustLevel = true;
                return _trustLevel;
            }

            _trustLevel = AspNetHostingPermissionLevel.None;
            _knowTrustLevel = true;
            return _trustLevel;
        }
    }
}