nullable fixes

Author: honfika

src/Titanium.Web.Proxy/EventArguments/SessionEventArgsBase.cs

@@ -22,7 +22,7 @@ public abstract class SessionEventArgsBase : EventArgs, IDisposable
     {
         private static bool isWindowsAuthenticationSupported => RunTime.IsWindows;
 
-        internal readonly CancellationTokenSource CancellationTokenSource;
+        internal readonly CancellationTokenSource? CancellationTokenSource;
 
         internal TcpServerConnection ServerConnection => HttpClient.Connection;
 

src/Titanium.Web.Proxy/Network/Tcp/TcpConnectionFactory.cs

@@ -417,7 +417,7 @@ private async Task<TcpServerConnection> createServerConnection(string remoteHost
                 throw;
             }
 
-            return new TcpServerConnection(proxyServer, tcpClient)
+            return new TcpServerConnection(proxyServer, tcpClient, stream)
             {
                 UpStreamProxy = externalProxy,
                 UpStreamEndPoint = upStreamEndPoint,
@@ -426,8 +426,6 @@ private async Task<TcpServerConnection> createServerConnection(string remoteHost
                 IsHttps = isHttps,
                 NegotiatedApplicationProtocol = negotiatedApplicationProtocol,
                 UseUpstreamProxy = useUpstreamProxy,
-                StreamWriter = new HttpRequestWriter(stream, proxyServer.BufferPool),
-                Stream = stream,
                 Version = httpVersion
             };
         }

src/Titanium.Web.Proxy/Network/Tcp/TcpServerConnection.cs

@@ -15,12 +15,14 @@ namespace Titanium.Web.Proxy.Network.Tcp
     /// </summary>
     internal class TcpServerConnection : IDisposable
     {
-        internal TcpServerConnection(ProxyServer proxyServer, TcpClient tcpClient)
+        internal TcpServerConnection(ProxyServer proxyServer, TcpClient tcpClient, CustomBufferedStream stream)
         {
             this.tcpClient = tcpClient;
             LastAccess = DateTime.Now;
             this.proxyServer = proxyServer;
             this.proxyServer.UpdateServerConnectionCount(true);
+            StreamWriter = new HttpRequestWriter(stream, proxyServer.BufferPool);
+            Stream = stream;
         }
 
         private ProxyServer proxyServer { get; }
@@ -59,12 +61,12 @@ internal TcpServerConnection(ProxyServer proxyServer, TcpClient tcpClient)
         /// <summary>
         ///     Used to write lines to server
         /// </summary>
-        internal HttpRequestWriter? StreamWriter { get; set; }
+        internal HttpRequestWriter StreamWriter { get; }
 
         /// <summary>
         ///     Server stream
         /// </summary>
-        internal CustomBufferedStream? Stream { get; set; }
+        internal CustomBufferedStream Stream { get; }
 
         /// <summary>
         ///     Last time this connection was used

src/Titanium.Web.Proxy/ProxyServer.cs

@@ -55,7 +55,7 @@ public partial class ProxyServer : IDisposable
         /// <summary>
         ///     Upstream proxy manager.
         /// </summary>
-        private WinHttpWebProxyFinder systemProxyResolver;
+        private WinHttpWebProxyFinder? systemProxyResolver;
 
 
         /// <inheritdoc />
@@ -421,7 +421,7 @@ public void SetAsSystemHttpsProxy(ExplicitProxyEndPoint endPoint)
         /// <param name="protocolType">The proxy protocol type.</param>
         public void SetAsSystemProxy(ExplicitProxyEndPoint endPoint, ProxyProtocolType protocolType)
         {
-            if (!RunTime.IsWindows)
+            if (systemProxySettingsManager == null)
             {
                 throw new NotSupportedException(@"Setting system proxy settings are only supported in Windows.
                             Please manually confugure you operating system to use this proxy's port and address.");
@@ -515,7 +515,7 @@ public void DisableSystemHttpsProxy()
         /// </summary>
         public void RestoreOriginalProxySettings()
         {
-            if (!RunTime.IsWindows)
+            if (systemProxySettingsManager == null)
             {
                 throw new NotSupportedException(@"Setting system proxy settings are only supported in Windows.
                             Please manually configure your operating system to use this proxy's port and address.");
@@ -529,7 +529,7 @@ public void RestoreOriginalProxySettings()
         /// </summary>
         public void DisableSystemProxy(ProxyProtocolType protocolType)
         {
-            if (!RunTime.IsWindows)
+            if (systemProxySettingsManager == null)
             {
                 throw new NotSupportedException(@"Setting system proxy settings are only supported in Windows.
                             Please manually configure your operating system to use this proxy's port and address.");
@@ -543,7 +543,7 @@ public void DisableSystemProxy(ProxyProtocolType protocolType)
         /// </summary>
         public void DisableAllSystemProxies()
         {
-            if (!RunTime.IsWindows)
+            if (systemProxySettingsManager == null)
             {
                 throw new NotSupportedException(@"Setting system proxy settings are only supported in Windows.
                             Please manually confugure you operating system to use this proxy's port and address.");
@@ -622,7 +622,7 @@ public void Stop()
                 throw new Exception("Proxy is not running.");
             }
 
-            if (RunTime.IsWindows && !RunTime.IsUwpOnWindows)
+            if (systemProxySettingsManager != null)
             {
                 bool setAsSystemProxy = ProxyEndPoints.OfType<ExplicitProxyEndPoint>()
                     .Any(x => x.IsSystemHttpProxy || x.IsSystemHttpsProxy);