Clean up events docs (#52607)

* Update snippets

* Fix ASP.NET references

* Misc

* Convert all snippets of article

* move snippets

* rewrite and adjust snippet refs

* Move to sensor example

* Rewrite multiple events article

* Remove redundant keywords

* Rewrite intro. Much better

* Clean up code a little

* Fix inline code

* Change titles from handle to declare

* minor edits

* Rename 'handle multiple' to 'declare multiple'

* Revert redirect

* fix redirects

* Fix title in toc

* Apply suggestion from @BillWagner

Co-authored-by: Bill Wagner <wiwagn@microsoft.com>

* Spacing in code

---------

Co-authored-by: Bill Wagner <wiwagn@microsoft.com>

Author: adegeo

.openpublishing.redirection.standard.json

@@ -403,6 +403,10 @@
             "source_path_from_root": "/docs/standard/events/how-to-consume-events-in-a-web-forms-application.md",
             "redirect_url": "/aspnet/web-forms/overview/how-to-consume-events"
         },
+        {
+            "source_path_from_root": "/docs/standard/events/how-to-handle-multiple-events-using-event-properties.md",
+            "redirect_url": "/dotnet/standard/events/how-to-declare-multiple-events-using-event-properties"
+        },
         {
             "source_path_from_root": "/docs/standard/exceptions.md",
             "redirect_url": "/dotnet/standard/exceptions/",

docs/fundamentals/toc.yml

@@ -341,8 +341,8 @@ items:
             displayName: events
           - name: Raise and consume events
             href: ../standard/events/how-to-raise-and-consume-events.md
-          - name: Handle multiple events using event properties
-            href: ../standard/events/how-to-handle-multiple-events-using-event-properties.md
+          - name: Declare multiple events using event properties
+            href: ../standard/events/how-to-declare-multiple-events-using-event-properties.md
           - name: Observer design pattern
             items:
               - name: Overview

docs/standard/events/how-to-declare-multiple-events-using-event-properties.md

@@ -0,0 +1,81 @@
+---
+title: "Declare multiple events using event properties"
+description: Learn how to declare many events by using event properties. Define delegate collections, event keys, and event properties. Implement add and remove accessor methods.
+ms.date: 03/25/2026
+ms.topic: how-to
+dev_langs:
+  - "csharp"
+  - "vb"
+helpviewer_keywords:
+  - "event properties [.NET]"
+  - "multiple events [.NET]"
+  - "event handling [.NET], with multiple events"
+  - "events [.NET], multiple"
+ai-usage: ai-assisted
+---
+
+# Declare multiple events using event properties
+
+When a class defines many events using field-like event declarations, the compiler generates a backing field for each one. Every instance of that class allocates memory for all of those fields—even for events that are never subscribed. With many events, this per-instance overhead wastes memory.
+
+To avoid this memory overhead, use event properties backed by a delegate collection. The collection must provide methods that set, access, and retrieve delegates by event key. <xref:System.ComponentModel.EventHandlerList> is designed for this purpose, but you can also use a <xref:System.Collections.Hashtable> or a class derived from <xref:System.Collections.DictionaryBase>. Keep the collection's implementation details private.
+
+Each event property defines an add accessor and a remove accessor. The add accessor adds the input delegate to the delegate collection, and the remove accessor removes it. Both accessors use a predefined key to add and remove instances from the collection.
+
+## Prerequisites
+
+Familiarize yourself with the concepts in the [Events](index.md) article.
+
+## Define multiple events using event properties
+
+These steps create a `Sensor` class that exposes 10 event properties, all backed by a single `EventHandlerList`.
+
+1. Define an event data class that inherits from <xref:System.EventArgs>.
+
+   Add properties for each piece of data you want to pass to the handler:
+
+   :::code language="csharp" source="./snippets/how-to-handle-multiple-events-using-event-properties/csharp/Sensor.cs" id="SensorEventArgs":::
+   :::code language="vb" source="./snippets/how-to-handle-multiple-events-using-event-properties/vb/Sensor.vb" id="SensorEventArgs":::
+
+1. Declare an <xref:System.ComponentModel.EventHandlerList> field to store the delegates:
+
+   :::code language="csharp" source="./snippets/how-to-handle-multiple-events-using-event-properties/csharp/Sensor.cs" id="EventHandlerListField":::
+   :::code language="vb" source="./snippets/how-to-handle-multiple-events-using-event-properties/vb/Sensor.vb" id="EventHandlerListField":::
+
+1. Declare a unique key for each event.
+
+   `EventHandlerList` stores delegates by key. Use a `static readonly` object (`Shared ReadOnly` in Visual Basic) for each key—object identity ensures each key is truly unique:
+
+   :::code language="csharp" source="./snippets/how-to-handle-multiple-events-using-event-properties/csharp/Sensor.cs" id="EventKeys":::
+   :::code language="vb" source="./snippets/how-to-handle-multiple-events-using-event-properties/vb/Sensor.vb" id="EventKeys":::
+
+1. Define each event as an event property with custom add and remove accessors.
+
+   Each accessor calls `AddHandler` or `RemoveHandler` on the list using that event's key. In C#, also add a `protected virtual` raise method that retrieves the delegate from the list by key and invokes it. In Visual Basic, the `Custom Event` declaration already includes a `RaiseEvent` block that does this:
+
+   :::code language="csharp" source="./snippets/how-to-handle-multiple-events-using-event-properties/csharp/Sensor.cs" id="SingleEventProperty":::
+   :::code language="vb" source="./snippets/how-to-handle-multiple-events-using-event-properties/vb/Sensor.vb" id="SingleEventProperty":::
+
+   Repeat this pattern for each event, using its corresponding key.
+
+1. Subscribe to the event using the `+=` operator (in Visual Basic, `AddHandler`):
+
+   :::code language="csharp" source="./snippets/how-to-handle-multiple-events-using-event-properties/csharp/Program.cs" id="SubscribeEvent":::
+   :::code language="vb" source="./snippets/how-to-handle-multiple-events-using-event-properties/vb/Program.vb" id="SubscribeEvent":::
+
+1. Define the event handler.
+
+   The signature must match the <xref:System.EventHandler`1> delegate—an `object` sender and your event data class as the second parameter:
+
+   :::code language="csharp" source="./snippets/how-to-handle-multiple-events-using-event-properties/csharp/Program.cs" id="HandleEvent":::
+   :::code language="vb" source="./snippets/how-to-handle-multiple-events-using-event-properties/vb/Program.vb" id="HandleEvent":::
+
+The following example shows the complete `Sensor` class implementation:
+
+:::code language="csharp" source="./snippets/how-to-handle-multiple-events-using-event-properties/csharp/Sensor.cs" id="EventProperties":::
+:::code language="vb" source="./snippets/how-to-handle-multiple-events-using-event-properties/vb/Sensor.vb" id="EventProperties":::
+
+## Related content
+
+- <xref:System.ComponentModel.EventHandlerList?displayProperty=nameWithType>
+- [Events](index.md)