Ios fix missing method exception

.gitignore

@@ -7,3 +7,4 @@ build/
 *.xam
 packages
 .vs
+*Resource.designer.cs

ModernHttpClient.nuspec

@@ -1,7 +1,7 @@
 <?xml version="1.0"?>
 <package xmlns="http://schemas.microsoft.com/packaging/2011/08/nuspec.xsd">
   <metadata>
-    <version>2.5.1</version>
+    <version>2.6.0</version>
     <authors>Switch Media, Paul Betts</authors>
     <owners>Switch Media, Paul Betts</owners>
     <licenseUrl>https://github.com/paulcbetts/ModernHttpClient/blob/master/COPYING</licenseUrl>

src/ModernHttpClient/iOS/NSUrlSessionHandler.cs

@@ -54,20 +54,25 @@ public class NativeMessageHandler : HttpClientHandler
         public bool DisableCaching { get; set; }
 
         public NativeMessageHandler(): this(false, false) { }
-        public NativeMessageHandler(bool throwOnCaptiveNetwork, bool customSSLVerification, NativeCookieHandler cookieHandler = null, SslProtocol? minimumSSLProtocol = null)
+        public NativeMessageHandler(bool throwOnCaptiveNetwork, bool customSSLVerification, NativeCookieHandler cookieHandler = null)
         {
             var configuration = NSUrlSessionConfiguration.DefaultSessionConfiguration;
 
             // System.Net.ServicePointManager.SecurityProtocol provides a mechanism for specifying supported protocol types
             // for System.Net. Since iOS only provides an API for a minimum and maximum protocol we are not able to port
             // this configuration directly and instead use the specified minimum value when one is specified.
-            if (minimumSSLProtocol.HasValue) {
-                configuration.TLSMinimumSupportedProtocol = minimumSSLProtocol.Value;
-            }
-
-            session = NSUrlSession.FromConfiguration(
-                NSUrlSessionConfiguration.DefaultSessionConfiguration, 
-                new DataTaskDelegate(this), null);
+            var sp = ServicePointManager.SecurityProtocol;
+            if ((sp & SecurityProtocolType.Ssl3) != 0)
+                configuration.TLSMinimumSupportedProtocol = SslProtocol.Ssl_3_0;
+            else if ((sp & SecurityProtocolType.Tls) != 0)
+                configuration.TLSMinimumSupportedProtocol = SslProtocol.Tls_1_0;
+            else if ((sp & SecurityProtocolType.Tls11) != 0)
+                configuration.TLSMinimumSupportedProtocol = SslProtocol.Tls_1_1;
+            else if ((sp & SecurityProtocolType.Tls12) != 0)
+                configuration.TLSMinimumSupportedProtocol = SslProtocol.Tls_1_2;
+
+            INSUrlSessionDelegate sessionDelegate = new DataTaskDelegate (this);
+            session = NSUrlSession.FromConfiguration (NSUrlSessionConfiguration.DefaultSessionConfiguration, sessionDelegate, null);
 
             this.throwOnCaptiveNetwork = throwOnCaptiveNetwork;
             this.customSSLVerification = customSSLVerification;