From 64ffc64a0d487e9cc7848a723cd40ffc8481d81c Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Thu, 26 Dec 2024 23:21:23 +1100
Subject: [PATCH] Add Delegate.HasSingleTarget (#270)

---
 apiCount.include.md                 |  2 +-
 api_list.include.md                 |  5 +++++
 readme.md                           |  7 ++++++-
 src/Polyfill/Polyfill_Delegate.cs   | 26 ++++++++++++++++++++++++++
 src/Tests/PolyfillTests_Delegate.cs | 23 +++++++++++++++++++++++
 5 files changed, 61 insertions(+), 2 deletions(-)
 create mode 100644 src/Polyfill/Polyfill_Delegate.cs
 create mode 100644 src/Tests/PolyfillTests_Delegate.cs

diff --git a/apiCount.include.md b/apiCount.include.md
index 155e0e8..daf25ed 100644
--- a/apiCount.include.md
+++ b/apiCount.include.md
@@ -1 +1 @@
-**API count: 433**
\ No newline at end of file
+**API count: 434**
\ No newline at end of file
diff --git a/api_list.include.md b/api_list.include.md
index 8c1e9d4..ac830ce 100644
--- a/api_list.include.md
+++ b/api_list.include.md
@@ -68,6 +68,11 @@
  * `bool TryFormat(decimal, Span<char>, int, ReadOnlySpan<char>, IFormatProvider?)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.decimal.tryformat#system-decimal-tryformat(system-span((system-char))-system-int32@-system-readonlyspan((system-char))-system-iformatprovider))
 
 
+#### Delegate
+
+ * `bool HasSingleTarget(Delegate)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.delegate.hassingletarget)
+
+
 #### Dictionary<TKey, TValue>
 
  * `bool Remove<TKey, TValue>(Dictionary<TKey, TValue>, TKey, TValue) where TKey : notnull` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2.remove)
diff --git a/readme.md b/readme.md
index 45fe5a6..f38179d 100644
--- a/readme.md
+++ b/readme.md
@@ -12,7 +12,7 @@ The package targets `netstandard2.0` and is designed to support the following ru
  * `net5.0`, `net6.0`, `net7.0`, `net8.0`, `net9.0`
 
 
-**API count: 433**<!-- singleLineInclude: apiCount. path: /apiCount.include.md -->
+**API count: 434**<!-- singleLineInclude: apiCount. path: /apiCount.include.md -->
 
 
 **See [Milestones](../../milestones?state=closed) for release notes.**
@@ -537,6 +537,11 @@ The class `Polyfill` includes the following extension methods:
  * `bool TryFormat(decimal, Span<char>, int, ReadOnlySpan<char>, IFormatProvider?)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.decimal.tryformat#system-decimal-tryformat(system-span((system-char))-system-int32@-system-readonlyspan((system-char))-system-iformatprovider))
 
 
+#### Delegate
+
+ * `bool HasSingleTarget(Delegate)` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.delegate.hassingletarget)
+
+
 #### Dictionary<TKey, TValue>
 
  * `bool Remove<TKey, TValue>(Dictionary<TKey, TValue>, TKey, TValue) where TKey : notnull` [reference](https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.dictionary-2.remove)
diff --git a/src/Polyfill/Polyfill_Delegate.cs b/src/Polyfill/Polyfill_Delegate.cs
new file mode 100644
index 0000000..048c2a0
--- /dev/null
+++ b/src/Polyfill/Polyfill_Delegate.cs
@@ -0,0 +1,26 @@
+// <auto-generated />
+
+using System.Runtime.CompilerServices;
+
+#pragma warning disable
+
+namespace Polyfills;
+
+using System;
+using System.Collections.Concurrent;
+
+static partial class Polyfill
+{
+    /// <summary>
+    /// Gets a value that indicates whether the Delegate has a single invocation target.
+    /// </summary>
+    //Link: https://learn.microsoft.com/en-us/dotnet/api/system.delegate.hassingletarget
+    public static bool HasSingleTarget(this Delegate target)
+    {
+#if NET9_0_OR_GREATER
+        return target.HasSingleTarget;
+#else
+        return target.GetInvocationList().Length == 1;
+#endif
+    }
+}
diff --git a/src/Tests/PolyfillTests_Delegate.cs b/src/Tests/PolyfillTests_Delegate.cs
new file mode 100644
index 0000000..55fa753
--- /dev/null
+++ b/src/Tests/PolyfillTests_Delegate.cs
@@ -0,0 +1,23 @@
+partial class PolyfillTests
+{
+    public static event EventHandler? MyEvent;
+
+    [Test]
+    public void HasSingleTarget()
+    {
+        MyEvent += Handler;
+        Assert.IsTrue(MyEvent.HasSingleTarget());
+        MyEvent += Handler;
+        Assert.IsFalse(MyEvent.HasSingleTarget());
+        var action = () =>
+        {
+        };
+        Assert.IsTrue(action.HasSingleTarget());
+        action += action;
+        Assert.IsFalse(action.HasSingleTarget());
+    }
+
+    static void Handler(object? sender, EventArgs e)
+    {
+    }
+}
\ No newline at end of file