Backport changes for initial metrics enablement #3575 (#3718)

Author: edwardneal

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/Diagnostics/SqlClientMetrics.cs

@@ -92,14 +92,19 @@ internal sealed partial class SqlClientMetrics
         private string? _instanceName;
 #endif
 
-        public SqlClientMetrics(SqlClientEventSource eventSource)
+        public SqlClientMetrics(SqlClientEventSource eventSource, bool enableMetrics)
         {
             _eventSource = eventSource;
 
 #if NETFRAMEWORK
             // On .NET Framework, metrics are exposed as performance counters and are always enabled.
             // On .NET Core, metrics are exposed as EventCounters, and require explicit enablement.
             EnablePerformanceCounters();
+#else
+            if (enableMetrics)
+            {
+                EnableEventCounters();
+            }
 #endif
         }
 

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/SqlClientEventSource.cs

@@ -15,11 +15,13 @@ namespace Microsoft.Data.SqlClient
     [EventSource(Name = "Microsoft.Data.SqlClient.EventSource")]
     internal partial class SqlClientEventSource : EventSource
     {
+        private static bool s_initialMetricsEnabled = false;
+
         // Defines the singleton instance for the Resources ETW provider
         public static readonly SqlClientEventSource Log = new();
 
         // Provides access to metrics.
-        public static readonly SqlClientMetrics Metrics = new SqlClientMetrics(Log);
+        public static readonly SqlClientMetrics Metrics = new SqlClientMetrics(Log, s_initialMetricsEnabled);
 
         private SqlClientEventSource() { }
 
@@ -33,7 +35,14 @@ protected override void OnEventCommand(EventCommandEventArgs command)
 
             if (command.Command == EventCommand.Enable)
             {
-                Metrics.EnableEventCounters();
+                if (Metrics == null)
+                {
+                    s_initialMetricsEnabled = true;
+                }
+                else
+                {
+                    Metrics.EnableEventCounters();
+                }
             }
         }
 #endif