From 787aed403f824b21c264336fd21ef46e291fcbc9 Mon Sep 17 00:00:00 2001
From: martincostello <martin@martincostello.com>
Date: Sat, 30 May 2020 21:13:45 +0100
Subject: [PATCH 1/2] Reuse model binders

Reuse the same model binders for CancellationTokens and services, rather than allocating a new one for every request with such a parameter.
---
 .../Binders/CancellationTokenModelBinderProvider.cs           | 4 +++-
 .../src/ModelBinding/Binders/ServicesModelBinderProvider.cs   | 4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/Mvc/Mvc.Core/src/ModelBinding/Binders/CancellationTokenModelBinderProvider.cs b/src/Mvc/Mvc.Core/src/ModelBinding/Binders/CancellationTokenModelBinderProvider.cs
index b3ee6f736112..e5e300c87ea8 100644
--- a/src/Mvc/Mvc.Core/src/ModelBinding/Binders/CancellationTokenModelBinderProvider.cs
+++ b/src/Mvc/Mvc.Core/src/ModelBinding/Binders/CancellationTokenModelBinderProvider.cs
@@ -11,6 +11,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
     /// </summary>
     public class CancellationTokenModelBinderProvider : IModelBinderProvider
     {
+        private CancellationTokenModelBinder _modelBinder;
+
         /// <inheritdoc />
         public IModelBinder GetBinder(ModelBinderProviderContext context)
         {
@@ -21,7 +23,7 @@ public IModelBinder GetBinder(ModelBinderProviderContext context)
 
             if (context.Metadata.ModelType == typeof(CancellationToken))
             {
-                return new CancellationTokenModelBinder();
+                return _modelBinder ??= new CancellationTokenModelBinder();
             }
 
             return null;
diff --git a/src/Mvc/Mvc.Core/src/ModelBinding/Binders/ServicesModelBinderProvider.cs b/src/Mvc/Mvc.Core/src/ModelBinding/Binders/ServicesModelBinderProvider.cs
index 2dea775a0a12..18c46192ec4c 100644
--- a/src/Mvc/Mvc.Core/src/ModelBinding/Binders/ServicesModelBinderProvider.cs
+++ b/src/Mvc/Mvc.Core/src/ModelBinding/Binders/ServicesModelBinderProvider.cs
@@ -10,6 +10,8 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
     /// </summary>
     public class ServicesModelBinderProvider : IModelBinderProvider
     {
+        private ServicesModelBinder _modelBinder;
+
         /// <inheritdoc />
         public IModelBinder GetBinder(ModelBinderProviderContext context)
         {
@@ -21,7 +23,7 @@ public IModelBinder GetBinder(ModelBinderProviderContext context)
             if (context.BindingInfo.BindingSource != null &&
                 context.BindingInfo.BindingSource.CanAcceptDataFrom(BindingSource.Services))
             {
-                return new ServicesModelBinder();
+                return _modelBinder ??= new ServicesModelBinder();
             }
 
             return null;

From 00108c94576866846e35b4dfda0a35be185784bb Mon Sep 17 00:00:00 2001
From: martincostello <martin@martincostello.com>
Date: Wed, 3 Jun 2020 14:57:23 +0100
Subject: [PATCH 2/2] Make fields readonly

Make the fields backing the binder once when initialized, rather than on first use.

Co-Authored-By: Pranav K <pranavkm@users.noreply.github.com>
---
 .../Binders/CancellationTokenModelBinderProvider.cs         | 6 ++++--
 .../src/ModelBinding/Binders/ServicesModelBinderProvider.cs | 6 ++++--
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/Mvc/Mvc.Core/src/ModelBinding/Binders/CancellationTokenModelBinderProvider.cs b/src/Mvc/Mvc.Core/src/ModelBinding/Binders/CancellationTokenModelBinderProvider.cs
index e5e300c87ea8..6819805276de 100644
--- a/src/Mvc/Mvc.Core/src/ModelBinding/Binders/CancellationTokenModelBinderProvider.cs
+++ b/src/Mvc/Mvc.Core/src/ModelBinding/Binders/CancellationTokenModelBinderProvider.cs
@@ -11,7 +11,9 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
     /// </summary>
     public class CancellationTokenModelBinderProvider : IModelBinderProvider
     {
-        private CancellationTokenModelBinder _modelBinder;
+        // CancellationTokenModelBinder does not have any state. Re-use the same instance for binding.
+
+        private readonly CancellationTokenModelBinder _modelBinder = new CancellationTokenModelBinder();
 
         /// <inheritdoc />
         public IModelBinder GetBinder(ModelBinderProviderContext context)
@@ -23,7 +25,7 @@ public IModelBinder GetBinder(ModelBinderProviderContext context)
 
             if (context.Metadata.ModelType == typeof(CancellationToken))
             {
-                return _modelBinder ??= new CancellationTokenModelBinder();
+                return _modelBinder;
             }
 
             return null;
diff --git a/src/Mvc/Mvc.Core/src/ModelBinding/Binders/ServicesModelBinderProvider.cs b/src/Mvc/Mvc.Core/src/ModelBinding/Binders/ServicesModelBinderProvider.cs
index 18c46192ec4c..b09d625c4dca 100644
--- a/src/Mvc/Mvc.Core/src/ModelBinding/Binders/ServicesModelBinderProvider.cs
+++ b/src/Mvc/Mvc.Core/src/ModelBinding/Binders/ServicesModelBinderProvider.cs
@@ -10,7 +10,9 @@ namespace Microsoft.AspNetCore.Mvc.ModelBinding.Binders
     /// </summary>
     public class ServicesModelBinderProvider : IModelBinderProvider
     {
-        private ServicesModelBinder _modelBinder;
+        // ServicesModelBinder does not have any state. Re-use the same instance for binding.
+
+        private readonly ServicesModelBinder _modelBinder = new ServicesModelBinder();
 
         /// <inheritdoc />
         public IModelBinder GetBinder(ModelBinderProviderContext context)
@@ -23,7 +25,7 @@ public IModelBinder GetBinder(ModelBinderProviderContext context)
             if (context.BindingInfo.BindingSource != null &&
                 context.BindingInfo.BindingSource.CanAcceptDataFrom(BindingSource.Services))
             {
-                return _modelBinder ??= new ServicesModelBinder();
+                return _modelBinder;
             }
 
             return null;