Added two new events - Closed and Opened

Toolkit.Foundation/Closed.cs

@@ -0,0 +1,9 @@
+namespace Toolkit.Foundation;
+
+public record Closed
+{
+    public static ClosedEventArgs<TSender> As<TSender>(TSender sender) => new(sender);
+
+    public static ClosedEventArgs<TSender> As<TSender>() where TSender : new() => new(new TSender());
+}
+

Toolkit.Foundation/ClosedEventArgs.cs

@@ -0,0 +1,3 @@
+namespace Toolkit.Foundation;
+
+public record ClosedEventArgs<TSender>(TSender? Sender = default);

Toolkit.Foundation/Opened.cs

@@ -0,0 +1,8 @@
+namespace Toolkit.Foundation;
+
+public record Opened
+{
+    public static OpenedEventArgs<TSender> As<TSender>(TSender sender) => new(sender);
+
+    public static OpenedEventArgs<TSender> As<TSender>() where TSender : new() => new(new TSender());
+}

Toolkit.Foundation/OpenedEventArgs.cs

@@ -0,0 +1,3 @@
+namespace Toolkit.Foundation;
+
+public record OpenedEventArgs<TSender>(TSender? Sender = default);