Fix(device): Fix issue with .NET standard 5 preview -> Not supported …

…exceptions. Fixes #1592 (#1594)

iothub/device/src/Common/Utils.cs

@@ -2,7 +2,10 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.IO;
+using System.Linq;
 using System.Text;
 using Microsoft.Azure.Devices.Client.Extensions;
 using Newtonsoft.Json;
@@ -106,5 +109,20 @@ public static void ValidateDataIsEmptyOrJson(byte[] data)
                 }
             }
         }
+
+        public static IReadOnlyDictionary<TKey, TValue> MergeDictionaries<TKey, TValue>(IDictionary<TKey, TValue>[] dictionaries)
+        {
+            // No item in the array should be null.
+            if (dictionaries == null || dictionaries.Any(item => item == null))
+            {
+                throw new ArgumentNullException(nameof(dictionaries), "Provided dictionaries should not be null");
+            }
+
+            Dictionary<TKey, TValue> result = dictionaries.SelectMany(dict => dict)
+                .ToLookup(pair => pair.Key, pair => pair.Value)
+                .ToDictionary(group => group.Key, group => group.First());
+
+            return new ReadOnlyDictionary<TKey, TValue>(result);
+        }
     }
 }

iothub/device/src/Transport/Mqtt/MqttIotHubAdapter.cs

@@ -1237,7 +1237,7 @@ public static async Task WriteMessageAsync(IChannelHandlerContext context, objec
             }
         }
 
-        internal string PopulateMessagePropertiesFromMessage(string topicName, Message message)
+        internal static string PopulateMessagePropertiesFromMessage(string topicName, Message message)
         {
             var systemProperties = new Dictionary<string, string>();
             foreach (KeyValuePair<string, object> property in message.SystemProperties)
@@ -1247,7 +1247,7 @@ internal string PopulateMessagePropertiesFromMessage(string topicName, Message m
                     systemProperties[propertyName] = ConvertFromSystemProperties(property.Value);
                 }
             }
-            string properties = UrlEncodedDictionarySerializer.Serialize(new ReadOnlyMergeDictionary<string, string>(systemProperties, message.Properties));
+            string properties = UrlEncodedDictionarySerializer.Serialize(Utils.MergeDictionaries(new IDictionary<string, string>[] { systemProperties, message.Properties }));
 
             string msg = properties.Length != 0
                 ? topicName.EndsWith(SegmentSeparator, StringComparison.Ordinal) ? topicName + properties + SegmentSeparator : topicName + SegmentSeparator + properties

iothub/device/tests/UtilsTests.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System;
+using System.Collections.Generic;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 
 namespace Microsoft.Azure.Devices.Client.Test
@@ -35,5 +36,64 @@ public void ConvertDeliveryAckTypeToStringInvalidValueFail()
         {
             Utils.ConvertDeliveryAckTypeToString((DeliveryAcknowledgement)100500);
         }
+
+        [TestMethod]
+        [ExpectedException(typeof(ArgumentNullException))]
+        public void MergeDictionaries_OneItemInListIsNull()
+        {
+            var dict1 = new Dictionary<int, string> { { 1, "One" }, { 2, "Two" }, { 3, "Three" } };
+
+            Utils.MergeDictionaries(new Dictionary<int, string>[] { dict1, null });
+        }
+
+        [TestMethod]
+        public void MergeDictionaries_TwoDictionaries_NoOverlap()
+        {
+            var dict1 = new Dictionary<int, string> { { 1, "One" }, { 2, "Two" }, { 3, "Three" } };
+            var dict2 = new Dictionary<int, string> { { 4, "Four" }, { 5, "Five" }, { 6, "Six" } };
+
+            var result = Utils.MergeDictionaries(new Dictionary<int, string>[] { dict1, dict2 });
+
+            Assert.AreEqual(6, result.Count, $"Number of items in the merged dictionary should be equal to {dict1.Count + dict2.Count}");
+        }
+
+        [TestMethod]
+        public void MergeDictionaries_ThreeDictionaries_NoOverlap()
+        {
+            var dict1 = new Dictionary<int, string> { { 1, "One" }, { 2, "Two" }, { 3, "Three" } };
+            var dict2 = new Dictionary<int, string> { { 4, "Four" }, { 5, "Five" }, { 6, "Six" } };
+            var dict3 = new Dictionary<int, string> { { 7, "Seven" }, { 8, "Eight" }, { 9, "Nine" } };
+
+            var result = Utils.MergeDictionaries(new Dictionary<int, string>[] { dict1, dict2, dict3 });
+
+            Assert.AreEqual(9, result.Count, $"Number of items in the merged dictionary should be equal to {dict1.Count + dict2.Count + dict3.Count}");
+        }
+
+        [TestMethod]
+        public void MergeDictionaries_TwoDictionaries_OneOverLap_PicksFirst()
+        {
+            var dict1 = new Dictionary<int, string> { { 1, "One" }, { 2, "Two" }, { 3, "Three" } };
+            var dict2 = new Dictionary<int, string> { { 1, "One1" }, { 4, "Four" }, { 5, "Five" } };
+
+            var result = Utils.MergeDictionaries(new Dictionary<int, string>[] { dict1, dict2 });
+
+            // There is one overlapping pair, we should pick the first one.
+            Assert.AreEqual(5, result.Count, $"Number of items in the merged dictionary should be equal to {dict1.Count + dict2.Count - 1}");
+            Assert.AreEqual(dict1[1], result[1], $"The first item in the list takes priority");
+        }
+
+        [TestMethod]
+        public void MergeDictionaries_ThreeDictionaries_OneOverLap_PicksFirst()
+        {
+            var dict1 = new Dictionary<int, string> { { 1, "One" }, { 2, "Two" }, { 3, "Three" } };
+            var dict2 = new Dictionary<int, string> { { 1, "One1" }, { 4, "Four" }, { 5, "Five" } };
+            var dict3 = new Dictionary<int, string> { { 1, "One2" }, { 6, "Six" }, { 7, "Seven" } };
+
+            var result = Utils.MergeDictionaries(new Dictionary<int, string>[] { dict1, dict2, dict3 });
+
+            // There is one overlapping pair, we should pick the first one.
+            Assert.AreEqual(7, result.Count, $"Number of items in the merged dictionary should be equal to {dict1.Count + dict2.Count + dict3.Count - 2}");
+            Assert.AreEqual(dict1[1], result[1], $"The first item in the list takes priority");
+        }
     }
 }