XmlUrlResolver.cs

using System.IO;
using System.Net;
using System.Net.Cache;
using System.Security.Permissions;
using System.Threading;
using System.Threading.Tasks;

namespace System.Xml
{
    public class XmlUrlResolver : XmlResolver
    {
        private static object s_DownloadManager;

        private ICredentials _credentials;

        private IWebProxy _proxy;

        private RequestCachePolicy _cachePolicy;

        private static XmlDownloadManager DownloadManager
        {
            get
            {
                if (s_DownloadManager == null)
                {
                    object value = new XmlDownloadManager();
                    Interlocked.CompareExchange<object>(ref s_DownloadManager, value, (object)null);
                }
                return (XmlDownloadManager)s_DownloadManager;
            }
        }

        public override ICredentials Credentials
        {
            set
            {
                _credentials = value;
            }
        }

        public IWebProxy Proxy
        {
            set
            {
                _proxy = value;
            }
        }

        public RequestCachePolicy CachePolicy
        {
            set
            {
                _cachePolicy = value;
            }
        }

        public override object GetEntity(Uri absoluteUri, string role, Type ofObjectToReturn)
        {
            if (ofObjectToReturn == null || ofObjectToReturn == typeof(Stream) || ofObjectToReturn == typeof(object))
            {
                return DownloadManager.GetStream(absoluteUri, _credentials, _proxy, _cachePolicy);
            }
            throw new XmlException("Xml_UnsupportedClass", string.Empty);
        }

        [PermissionSet(SecurityAction.InheritanceDemand, Name = "FullTrust")]
        public override Uri ResolveUri(Uri baseUri, string relativeUri)
        {
            return base.ResolveUri(baseUri, relativeUri);
        }

        public override async Task<object> GetEntityAsync(Uri absoluteUri, string role, Type ofObjectToReturn)
        {
            if (ofObjectToReturn == null || ofObjectToReturn == typeof(Stream) || ofObjectToReturn == typeof(object))
            {
                return await DownloadManager.GetStreamAsync(absoluteUri, _credentials, _proxy, _cachePolicy).ConfigureAwait(continueOnCapturedContext: false);
            }
            throw new XmlException("Xml_UnsupportedClass", string.Empty);
        }
    }
}