Optimization: make event arguments readonly structs

Author: SergeiPavlov

Extensions/Xtensive.Orm.Reprocessing/DomainBuildErrorEventArgs.cs

@@ -1,12 +1,24 @@
-using System;
+// Copyright (C) 2003-2022 Xtensive LLC.
+// This code is distributed under MIT license terms.
+// See the License.txt file in the project root for more information.
+using System;
 
 namespace Xtensive.Orm.Reprocessing
 {
   /// <summary>
   /// Contains <see cref="ReprocessableDomainBuilder.Error"/> event data.
   /// </summary>
-  public class DomainBuildErrorEventArgs : EventArgs
+  public readonly struct DomainBuildErrorEventArgs
   {
+    /// <summary>
+    /// Gets the exception.
+    /// </summary>
+    public Exception Exception { get; }
+    /// <summary>
+    /// Gets the attempt number.
+    /// </summary>
+    public int Attempt { get; }
+
     /// <summary>
     /// Initializes a new instance of the <see cref="DomainBuildErrorEventArgs"/> class.
     /// </summary>
@@ -17,14 +29,5 @@ public DomainBuildErrorEventArgs(Exception exception, int attempt)
       Exception = exception;
       Attempt = attempt;
     }
-
-    /// <summary>
-    /// Gets the exception.
-    /// </summary>
-    public Exception Exception { get; private set; }
-    /// <summary>
-    /// Gets the attempt number.
-    /// </summary>
-    public int Attempt { get; private set; }
   }
 }

Extensions/Xtensive.Orm.Reprocessing/ExecuteErrorEventArgs.cs

@@ -1,31 +1,35 @@
-using System;
+// Copyright (C) 2003-2022 Xtensive LLC.
+// This code is distributed under MIT license terms.
+// See the License.txt file in the project root for more information.
+
+using System;
 
 namespace Xtensive.Orm.Reprocessing
 {
   /// <summary>
   /// Provides data for the <see cref="IExecuteActionStrategy.Error"/> event
   /// </summary>
-  public class ExecuteErrorEventArgs : EventArgs
+  public readonly struct ExecuteErrorEventArgs
   {
     /// <summary>
     /// Gets the attempt number of this task.
     /// </summary>
-    public int Attempt { get; private set; }
+    public int Attempt { get; }
 
     /// <summary>
     /// Gets the exception of this task.
     /// </summary>
-    public Exception Exception { get; private set; }
+    public Exception Exception { get; }
 
     /// <summary>
     /// Gets the session of this task. Session will have outer transaction.
     /// </summary>
-    public Session Session { get; private set; }
+    public Session Session { get; }
 
     /// <summary>
     /// Gets the transaction of this task.
     /// </summary>
-    public Transaction Transaction { get; private set; }
+    public Transaction Transaction { get; }
 
     /// <summary>
     /// Initializes a new instance of the <see cref="ExecuteErrorEventArgs"/> class.
@@ -42,4 +46,4 @@ public ExecuteErrorEventArgs(Exception exception, Session session, Transaction t
       Transaction = transaction;
     }
   }
-}
+}

Extensions/Xtensive.Orm.Tracking/TrackingCompletedEventArgs.cs

@@ -1,4 +1,4 @@
-// Copyright (C) 2019-2020 Xtensive LLC.
+// Copyright (C) 2019-2022 Xtensive LLC.
 // This code is distributed under MIT license terms.
 // See the License.txt file in the project root for more information.
 
@@ -10,17 +10,17 @@ namespace Xtensive.Orm.Tracking
   /// <summary>
   /// Event arguments for <see cref="ITrackingMonitor.TrackingCompleted"/> event.
   /// </summary>
-  public sealed class TrackingCompletedEventArgs : EventArgs
+  public readonly struct TrackingCompletedEventArgs
   {
     /// <summary>
     /// Gets session this changes occured in.
     /// </summary>
-    public Session Session { get; private set; }
+    public Session Session { get; }
 
     /// <summary>
     /// Gets the changes.
     /// </summary>
-    public IEnumerable<ITrackingItem> Changes { get; private set; }
+    public IEnumerable<ITrackingItem> Changes { get; }
 
     /// <summary>
     /// Initializes a new instance of the <see cref="TrackingCompletedEventArgs"/> class.
@@ -30,13 +30,8 @@ public sealed class TrackingCompletedEventArgs : EventArgs
     /// <param name="changes">The changes.</param>
     public TrackingCompletedEventArgs(Session session, IEnumerable<ITrackingItem> changes)
     {
-      if (session==null)
-        throw new ArgumentNullException("session");
-      if (changes == null)
-        throw new ArgumentNullException("changes");
-
-      Session = session;
-      Changes = changes;
+      Session = session ?? throw new ArgumentNullException("session");
+      Changes = changes ?? throw new ArgumentNullException("changes");
     }
   }
 }