Add ActivitySource Tags

src/libraries/Common/src/System/Diagnostics/DiagnosticsHelper.cs

@@ -19,7 +19,7 @@ internal static class DiagnosticsHelper
         /// we avoid the allocation of a new array by using the second collection as is and not converting it to an array. the reason
         /// is we call this every time we try to create a meter or instrument and we don't want to allocate a new array every time.
         /// </remarks>
-        internal static bool CompareTags(List<KeyValuePair<string, object?>>? sortedTags, IEnumerable<KeyValuePair<string, object?>>? tags2)
+        internal static bool CompareTags(IList<KeyValuePair<string, object?>>? sortedTags, IEnumerable<KeyValuePair<string, object?>>? tags2)
         {
             if (sortedTags == tags2)
             {

src/libraries/Microsoft.Extensions.Diagnostics/src/Metrics/DefaultMeterFactory.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Diagnostics;
 using System.Diagnostics.Metrics;
 
@@ -40,7 +41,7 @@ public Meter Create(MeterOptions options)
                 {
                     foreach (Meter meter in meterList)
                     {
-                        if (meter.Version == options.Version && DiagnosticsHelper.CompareTags(meter.Tags as List<KeyValuePair<string, object?>>, options.Tags))
+                        if (meter.Version == options.Version && DiagnosticsHelper.CompareTags(meter.Tags as IList<KeyValuePair<string, object?>>, options.Tags))
                         {
                             return meter;
                         }

src/libraries/System.Diagnostics.DiagnosticSource/ref/System.Diagnostics.DiagnosticSourceActivity.cs

@@ -150,9 +150,13 @@ public void CopyTo(System.Span<byte> destination) { }
     }
     public sealed class ActivitySource : IDisposable
     {
+        public ActivitySource(string name) { throw null; }
+        [System.ComponentModel.EditorBrowsable(System.ComponentModel.EditorBrowsableState.Never)]
         public ActivitySource(string name, string? version = "") { throw null; }
+        public ActivitySource(string name, string? version = "", System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object?>>? tags = default) { throw null; }
         public string Name { get { throw null; } }
         public string? Version { get { throw null; } }
+        public System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object?>>? Tags { get { throw null; } }
         public bool HasListeners() { throw null; }
         public System.Diagnostics.Activity? CreateActivity(string name, System.Diagnostics.ActivityKind kind) { throw null; }
         public System.Diagnostics.Activity? CreateActivity(string name, System.Diagnostics.ActivityKind kind, System.Diagnostics.ActivityContext parentContext, System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object?>>? tags = null, System.Collections.Generic.IEnumerable<System.Diagnostics.ActivityLink>? links = null, System.Diagnostics.ActivityIdFormat idFormat = System.Diagnostics.ActivityIdFormat.Unknown) { throw null; }

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/ActivitySource.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Collections.Generic;
+using System.ComponentModel;
 using System.Runtime.CompilerServices;
 using System.Threading;
 
@@ -13,16 +14,40 @@ public sealed class ActivitySource : IDisposable
         private static readonly SynchronizedList<ActivityListener> s_allListeners = new SynchronizedList<ActivityListener>();
         private SynchronizedList<ActivityListener>? _listeners;
 
+        /// <summary>
+        /// Construct an ActivitySource object with the input name
+        /// </summary>
+        /// <param name="name">The name of the ActivitySource object</param>
+        public ActivitySource(string name) : this(name, version: "", tags: null) {}
+
         /// <summary>
         /// Construct an ActivitySource object with the input name
         /// </summary>
         /// <param name="name">The name of the ActivitySource object</param>
         /// <param name="version">The version of the component publishing the tracing info.</param>
-        public ActivitySource(string name, string? version = "")
+        [EditorBrowsable(EditorBrowsableState.Never)]
+        public ActivitySource(string name, string? version = "") : this(name, version, tags: null) {}
+
+        /// <summary>
+        /// Construct an ActivitySource object with the input name
+        /// </summary>
+        /// <param name="name">The name of the ActivitySource object</param>
+        /// <param name="version">The version of the component publishing the tracing info.</param>
+        /// <param name="tags">The optional ActivitySource tags.</param>
+        public ActivitySource(string name, string? version = "", IEnumerable<KeyValuePair<string, object?>>? tags = default)
         {
             Name = name ?? throw new ArgumentNullException(nameof(name));
             Version = version;
 
+            // Sorting the tags to make sure the tags are always in the same order.
+            // Sorting can help in comparing the tags used for any scenario.
+            if (tags is not null)
+            {
+                var tagList = new List<KeyValuePair<string, object?>>(tags);
+                tagList.Sort((left, right) => string.Compare(left.Key, right.Key, StringComparison.Ordinal));
+                Tags = tagList.AsReadOnly();
+            }
+
             s_activeSources.Add(this);
 
             if (s_allListeners.Count > 0)
@@ -54,6 +79,11 @@ public ActivitySource(string name, string? version = "")
         /// </summary>
         public string? Version { get; }
 
+        /// <summary>
+        /// Returns the tags associated with the ActivitySource.
+        /// </summary>
+        public IEnumerable<KeyValuePair<string, object?>>? Tags { get; }
+
         /// <summary>
         /// Check if there is any listeners for this ActivitySource.
         /// This property can be helpful to tell if there is no listener, then no need to create Activity object

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Metrics/Meter.cs

@@ -79,7 +79,7 @@ private void Initialize(string name, string? version, IEnumerable<KeyValuePair<s
             {
                 var tagList = new List<KeyValuePair<string, object?>>(tags);
                 tagList.Sort((left, right) => string.Compare(left.Key, right.Key, StringComparison.Ordinal));
-                Tags = tagList;
+                Tags = tagList.AsReadOnly();
             }
             Scope = scope;
 

src/libraries/System.Diagnostics.DiagnosticSource/tests/ActivitySourceTests.cs

@@ -23,11 +23,20 @@ public void TestConstruction()
                 Assert.Equal("Source1", as1.Name);
                 Assert.Equal(String.Empty, as1.Version);
                 Assert.False(as1.HasListeners());
+                Assert.Null(as1.Tags);
 
                 using ActivitySource as2 =  new ActivitySource("Source2", "1.1.1.2");
                 Assert.Equal("Source2", as2.Name);
                 Assert.Equal("1.1.1.2", as2.Version);
                 Assert.False(as2.HasListeners());
+                Assert.Null(as2.Tags);
+
+                using ActivitySource as3 =  new ActivitySource("Source3", "1.1.1.3", new TagList { { "key3", "value3" }, { "key2", "value2" }, { "key1", "value1" } });
+                Assert.Equal("Source3", as3.Name);
+                Assert.Equal("1.1.1.3", as3.Version);
+                Assert.False(as3.HasListeners());
+                // Ensure the tags are sorted by key.
+                Assert.Equal(new TagList  { { "key1", "value1" }, { "key2", "value2" }, { "key3", "value3" } }, as3.Tags);
             }).Dispose();
         }