Added nullable annotations for the trace folder in the api project.

src/OpenTelemetry.Api/Trace/ActivityExtensions.cs

@@ -14,6 +14,8 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 using System.Diagnostics;
 using System.Runtime.CompilerServices;
 using OpenTelemetry.Internal;
@@ -41,10 +43,11 @@ public static class ActivityExtensions
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static void SetStatus(this Activity activity, Status status)
     {
-        Debug.Assert(activity != null, "Activity should not be null");
-
-        activity.SetTag(SpanAttributeConstants.StatusCodeKey, StatusHelper.GetTagValueForStatusCode(status.StatusCode));
-        activity.SetTag(SpanAttributeConstants.StatusDescriptionKey, status.Description);
+        if (activity != null)
+        {
+            activity.SetTag(SpanAttributeConstants.StatusCodeKey, StatusHelper.GetTagValueForStatusCode(status.StatusCode));
+            activity.SetTag(SpanAttributeConstants.StatusDescriptionKey, status.Description);
+        }
     }
 
     /// <summary>
@@ -57,7 +60,8 @@ public static void SetStatus(this Activity activity, Status status)
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
     public static Status GetStatus(this Activity activity)
     {
-        if (!activity.TryGetStatus(out StatusCode statusCode, out string statusDescription))
+        if (activity == null
+            || !activity.TryGetStatus(out var statusCode, out var statusDescription))
         {
             return Status.Unset;
         }
@@ -71,10 +75,8 @@ public static Status GetStatus(this Activity activity)
     /// <param name="activity">Activity instance.</param>
     /// <param name="ex">Exception to be recorded.</param>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static void RecordException(this Activity activity, Exception ex)
-    {
-        activity?.RecordException(ex, default);
-    }
+    public static void RecordException(this Activity activity, Exception? ex)
+        => RecordException(activity, ex, default);
 
     /// <summary>
     /// Adds an activity event containing information from the specified exception and additional tags.
@@ -83,7 +85,7 @@ public static void RecordException(this Activity activity, Exception ex)
     /// <param name="ex">Exception to be recorded.</param>
     /// <param name="tags">Additional tags to record on the event.</param>
     [MethodImpl(MethodImplOptions.AggressiveInlining)]
-    public static void RecordException(this Activity activity, Exception ex, in TagList tags)
+    public static void RecordException(this Activity activity, Exception? ex, in TagList tags)
     {
         if (ex == null || activity == null)
         {

src/OpenTelemetry.Api/Trace/IDeferredTracerProviderBuilder.cs

@@ -14,6 +14,8 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 namespace OpenTelemetry.Trace;
 
 /// <summary>

src/OpenTelemetry.Api/Trace/Link.cs

@@ -14,6 +14,8 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 using System.Diagnostics;
 
 namespace OpenTelemetry.Trace;
@@ -30,16 +32,16 @@ namespace OpenTelemetry.Trace;
     /// </summary>
     /// <param name="spanContext">Span context of a linked span.</param>
     public Link(in SpanContext spanContext)
+        : this(in spanContext, attributes: null)
     {
-        this.ActivityLink = new ActivityLink(spanContext.ActivityContext);
     }
 
     /// <summary>
     /// Initializes a new instance of the <see cref="Link"/> struct.
     /// </summary>
     /// <param name="spanContext">Span context of a linked span.</param>
     /// <param name="attributes">Link attributes.</param>
-    public Link(in SpanContext spanContext, SpanAttributes attributes)
+    public Link(in SpanContext spanContext, SpanAttributes? attributes)
     {
         this.ActivityLink = new ActivityLink(spanContext.ActivityContext, attributes?.Attributes);
     }
@@ -48,53 +50,39 @@ public Link(in SpanContext spanContext, SpanAttributes attributes)
     /// Gets the span context of a linked span.
     /// </summary>
     public SpanContext Context
-    {
-        get
-        {
-            return new SpanContext(this.ActivityLink.Context);
-        }
-    }
+        => new(this.ActivityLink.Context);
 
     /// <summary>
     /// Gets the collection of attributes associated with the link.
     /// </summary>
-    public IEnumerable<KeyValuePair<string, object>> Attributes
-    {
-        get
-        {
-            return this.ActivityLink.Tags;
-        }
-    }
+    public IEnumerable<KeyValuePair<string, object?>>? Attributes
+        => this.ActivityLink.Tags;
 
     /// <summary>
     /// Compare two <see cref="Link"/> for equality.
     /// </summary>
     /// <param name="link1">First link to compare.</param>
     /// <param name="link2">Second link to compare.</param>
-    public static bool operator ==(Link link1, Link link2) => link1.Equals(link2);
+    public static bool operator ==(Link link1, Link link2)
+        => link1.Equals(link2);
 
     /// <summary>
     /// Compare two <see cref="Link"/> for not equality.
     /// </summary>
     /// <param name="link1">First link to compare.</param>
     /// <param name="link2">Second link to compare.</param>
-    public static bool operator !=(Link link1, Link link2) => !link1.Equals(link2);
+    public static bool operator !=(Link link1, Link link2)
+        => !link1.Equals(link2);
 
     /// <inheritdoc />
-    public override bool Equals(object obj)
-    {
-        return (obj is Link link) && this.ActivityLink.Equals(link.ActivityLink);
-    }
+    public override bool Equals(object? obj)
+        => obj is Link link && this.ActivityLink.Equals(link.ActivityLink);
 
     /// <inheritdoc />
     public override int GetHashCode()
-    {
-        return this.ActivityLink.GetHashCode();
-    }
+        => this.ActivityLink.GetHashCode();
 
     /// <inheritdoc/>
     public bool Equals(Link other)
-    {
-        return this.ActivityLink.Equals(other.ActivityLink);
-    }
+        => this.ActivityLink.Equals(other.ActivityLink);
 }

src/OpenTelemetry.Api/Trace/SpanAttributes.cs

@@ -14,6 +14,8 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 using System.Diagnostics;
 using OpenTelemetry.Internal;
 
@@ -37,12 +39,12 @@ public SpanAttributes()
     /// Initializes a new instance of the <see cref="SpanAttributes"/> class.
     /// </summary>
     /// <param name="attributes">Initial attributes to store in the collection.</param>
-    public SpanAttributes(IEnumerable<KeyValuePair<string, object>> attributes)
+    public SpanAttributes(IEnumerable<KeyValuePair<string, object?>> attributes)
         : this()
     {
         Guard.ThrowIfNull(attributes);
 
-        foreach (KeyValuePair<string, object> kvp in attributes)
+        foreach (KeyValuePair<string, object?> kvp in attributes)
         {
             this.AddInternal(kvp.Key, kvp.Value);
         }
@@ -65,7 +67,7 @@ public void Add(string key, long value)
     /// </summary>
     /// <param name="key">Entry key.</param>
     /// <param name="value">Entry value.</param>
-    public void Add(string key, string value)
+    public void Add(string key, string? value)
     {
         this.AddInternal(key, value);
     }
@@ -95,7 +97,7 @@ public void Add(string key, double value)
     /// </summary>
     /// <param name="key">Entry key.</param>
     /// <param name="values">Entry value.</param>
-    public void Add(string key, long[] values)
+    public void Add(string key, long[]? values)
     {
         this.AddInternal(key, values);
     }
@@ -105,7 +107,7 @@ public void Add(string key, long[] values)
     /// </summary>
     /// <param name="key">Entry key.</param>
     /// <param name="values">Entry value.</param>
-    public void Add(string key, string[] values)
+    public void Add(string key, string?[]? values)
     {
         this.AddInternal(key, values);
     }
@@ -115,7 +117,7 @@ public void Add(string key, string[] values)
     /// </summary>
     /// <param name="key">Entry key.</param>
     /// <param name="values">Entry value.</param>
-    public void Add(string key, bool[] values)
+    public void Add(string key, bool[]? values)
     {
         this.AddInternal(key, values);
     }
@@ -125,12 +127,12 @@ public void Add(string key, bool[] values)
     /// </summary>
     /// <param name="key">Entry key.</param>
     /// <param name="values">Entry value.</param>
-    public void Add(string key, double[] values)
+    public void Add(string key, double[]? values)
     {
         this.AddInternal(key, values);
     }
 
-    private void AddInternal(string key, object value)
+    private void AddInternal(string key, object? value)
     {
         Guard.ThrowIfNull(key);
 

src/OpenTelemetry.Api/Trace/SpanContext.cs

@@ -13,6 +13,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 // </copyright>
+
+#nullable enable
+
 using System.Diagnostics;
 using OpenTelemetry.Context.Propagation;
 
@@ -39,7 +42,12 @@ namespace OpenTelemetry.Trace;
     /// associate with the <see cref="SpanContext"/>.</param>
     /// <param name="isRemote">The value indicating whether this <see cref="SpanContext"/> was propagated from the remote parent.</param>
     /// <param name="traceState">The traceState to associate with the <see cref="SpanContext"/>.</param>
-    public SpanContext(in ActivityTraceId traceId, in ActivitySpanId spanId, ActivityTraceFlags traceFlags, bool isRemote = false, IEnumerable<KeyValuePair<string, string>> traceState = null)
+    public SpanContext(
+        in ActivityTraceId traceId,
+        in ActivitySpanId spanId,
+        ActivityTraceFlags traceFlags,
+        bool isRemote = false,
+        IEnumerable<KeyValuePair<string, string>>? traceState = null)
     {
         this.ActivityContext = new ActivityContext(traceId, spanId, traceFlags, TraceStateUtilsNew.GetString(traceState), isRemote);
     }
@@ -57,46 +65,26 @@ public SpanContext(in ActivityContext activityContext)
     /// Gets the <see cref="ActivityTraceId"/> associated with this <see cref="SpanContext"/>.
     /// </summary>
     public ActivityTraceId TraceId
-    {
-        get
-        {
-            return this.ActivityContext.TraceId;
-        }
-    }
+        => this.ActivityContext.TraceId;
 
     /// <summary>
     /// Gets the <see cref="ActivitySpanId"/> associated with this <see cref="SpanContext"/>.
     /// </summary>
     public ActivitySpanId SpanId
-    {
-        get
-        {
-            return this.ActivityContext.SpanId;
-        }
-    }
+        => this.ActivityContext.SpanId;
 
     /// <summary>
     /// Gets the <see cref="ActivityTraceFlags"/> associated with this <see cref="SpanContext"/>.
     /// </summary>
     public ActivityTraceFlags TraceFlags
-    {
-        get
-        {
-            return this.ActivityContext.TraceFlags;
-        }
-    }
+        => this.ActivityContext.TraceFlags;
 
     /// <summary>
     /// Gets a value indicating whether this <see cref="SpanContext" />
     /// was propagated from a remote parent.
     /// </summary>
     public bool IsRemote
-    {
-        get
-        {
-            return this.ActivityContext.IsRemote;
-        }
-    }
+        => this.ActivityContext.IsRemote;
 
     /// <summary>
     /// Gets a value indicating whether this <see cref="SpanContext"/> is valid.
@@ -125,47 +113,40 @@ public IEnumerable<KeyValuePair<string, string>> TraceState
     /// Converts a <see cref="SpanContext"/> into an <see cref="ActivityContext"/>.
     /// </summary>
     /// <param name="spanContext"><see cref="SpanContext"/> source.</param>
-    public static implicit operator ActivityContext(SpanContext spanContext) => spanContext.ActivityContext;
+    public static implicit operator ActivityContext(SpanContext spanContext)
+        => spanContext.ActivityContext;
 
     /// <summary>
     /// Compare two <see cref="SpanContext"/> for equality.
     /// </summary>
     /// <param name="spanContext1">First SpanContext to compare.</param>
     /// <param name="spanContext2">Second SpanContext to compare.</param>
-    public static bool operator ==(SpanContext spanContext1, SpanContext spanContext2) => spanContext1.Equals(spanContext2);
+    public static bool operator ==(SpanContext spanContext1, SpanContext spanContext2)
+        => spanContext1.Equals(spanContext2);
 
     /// <summary>
     /// Compare two <see cref="SpanContext"/> for not equality.
     /// </summary>
     /// <param name="spanContext1">First SpanContext to compare.</param>
     /// <param name="spanContext2">Second SpanContext to compare.</param>
-    public static bool operator !=(SpanContext spanContext1, SpanContext spanContext2) => !spanContext1.Equals(spanContext2);
+    public static bool operator !=(SpanContext spanContext1, SpanContext spanContext2)
+        => !spanContext1.Equals(spanContext2);
 
     /// <inheritdoc/>
     public override int GetHashCode()
-    {
-        return this.ActivityContext.GetHashCode();
-    }
+        => this.ActivityContext.GetHashCode();
 
     /// <inheritdoc/>
-    public override bool Equals(object obj)
-    {
-        return (obj is SpanContext ctx) && this.ActivityContext.Equals(ctx.ActivityContext);
-    }
+    public override bool Equals(object? obj)
+        => obj is SpanContext ctx && this.Equals(ctx);
 
     /// <inheritdoc/>
     public bool Equals(SpanContext other)
-    {
-        return this.ActivityContext.Equals(other.ActivityContext);
-    }
+        => this.ActivityContext.Equals(other.ActivityContext);
 
     private static bool IsTraceIdValid(ActivityTraceId traceId)
-    {
-        return traceId != default;
-    }
+        => traceId != default;
 
     private static bool IsSpanIdValid(ActivitySpanId spanId)
-    {
-        return spanId != default;
-    }
+        => spanId != default;
 }

src/OpenTelemetry.Api/Trace/SpanKind.cs

@@ -14,6 +14,8 @@
 // limitations under the License.
 // </copyright>
 
+#nullable enable
+
 namespace OpenTelemetry.Trace;
 
 /// <summary>