# System.Diagnostics

``` diff
 namespace System.Diagnostics {
     public class Activity {
-        public ref readonly ActivitySpanId ParentSpanId { get; }
+        public ActivitySpanId ParentSpanId { get; }
-        public ref readonly ActivitySpanId SpanId { get; }
+        public ActivitySpanId SpanId { get; }
-        public ref readonly ActivityTraceId TraceId { get; }
+        public ActivityTraceId TraceId { get; }
+        public Activity SetIdFormat(ActivityIdFormat format);
-        public Activity SetParentId(in ActivityTraceId traceId, in ActivitySpanId spanId, ActivityTraceFlags activityTraceFlags = ActivityTraceFlags.None);
+        public Activity SetParentId(ActivityTraceId traceId, ActivitySpanId spanId, ActivityTraceFlags activityTraceFlags = ActivityTraceFlags.None);
     }
     public readonly struct ActivitySpanId : IEquatable<ActivitySpanId> {
-        public static bool operator ==(in ActivitySpanId spanId1, in ActivitySpanId spandId2);
+        public static bool operator ==(ActivitySpanId spanId1, ActivitySpanId spandId2);
-        public static bool operator !=(in ActivitySpanId spanId1, in ActivitySpanId spandId2);
+        public static bool operator !=(ActivitySpanId spanId1, ActivitySpanId spandId2);
     }
     public readonly struct ActivityTraceId : IEquatable<ActivityTraceId> {
-        public static bool operator ==(in ActivityTraceId traceId1, in ActivityTraceId traceId2);
+        public static bool operator ==(ActivityTraceId traceId1, ActivityTraceId traceId2);
-        public static bool operator !=(in ActivityTraceId traceId1, in ActivityTraceId traceId2);
+        public static bool operator !=(ActivityTraceId traceId1, ActivityTraceId traceId2);
     }
 }
```

