Using [NotNull]

src/Microsoft.AspNet.Cors.Core/CorsOptions.cs

@@ -23,13 +23,9 @@ namespace Microsoft.AspNet.Cors.Core
                 return _defaultPolicyName;
             }
 
+            [param: NotNull]
             set
             {
-                if (value == null)
-                {
-                    throw new ArgumentNullException("value");
-                }
-
                 _defaultPolicyName = value;
             }
         }

src/Microsoft.AspNet.Cors.Core/CorsPolicy.cs

@@ -96,7 +96,7 @@ namespace Microsoft.AspNet.Cors.Core
             {
                 if (value < TimeSpan.Zero)
                 {
-                    throw new ArgumentOutOfRangeException("value", Resources.PreflightMaxAgeOutOfRange);
+                    throw new ArgumentOutOfRangeException(nameof(value), Resources.PreflightMaxAgeOutOfRange);
                 }
 
                 _preflightMaxAge = value;

src/Microsoft.AspNet.Cors.Core/CorsResult.cs

@@ -59,7 +59,7 @@ namespace Microsoft.AspNet.Cors.Core
             {
                 if (value < TimeSpan.Zero)
                 {
-                    throw new ArgumentOutOfRangeException("value", Resources.PreflightMaxAgeOutOfRange);
+                    throw new ArgumentOutOfRangeException(nameof(value), Resources.PreflightMaxAgeOutOfRange);
                 }
                 _preflightMaxAge = value;
             }