From 7115907bf7a835bb4fd682d861dee59a044bae15 Mon Sep 17 00:00:00 2001
From: Simon Schulze <57634354+SSchulze1989@users.noreply.github.com>
Date: Sat, 11 Jun 2022 22:02:34 +0200
Subject: [PATCH] Add overload for Set<T>() with custom IEqualityComparer
 (#113)

---
 .../ViewModel/ViewModelBase.cs                | 10 ++++-
 .../ViewModel/ViewModelBaseTests.cs           | 39 ++++++++++++++++++-
 2 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/src/MvvmBlazor.Core/ViewModel/ViewModelBase.cs b/src/MvvmBlazor.Core/ViewModel/ViewModelBase.cs
index a8f48ac..140a599 100644
--- a/src/MvvmBlazor.Core/ViewModel/ViewModelBase.cs
+++ b/src/MvvmBlazor.Core/ViewModel/ViewModelBase.cs
@@ -1,4 +1,4 @@
-namespace MvvmBlazor.ViewModel;
+namespace MvvmBlazor.ViewModel;
 
 public abstract class ViewModelBase : INotifyPropertyChanged
 {
@@ -10,7 +10,13 @@ public abstract class ViewModelBase : INotifyPropertyChanged
 
     protected bool Set<T>(ref T field, T value, [CallerMemberName] string? propertyName = null)
     {
-        if (!EqualityComparer<T>.Default.Equals(field, value))
+        return Set(ref field, value, EqualityComparer<T>.Default, propertyName);
+    }
+
+    protected bool Set<T>(ref T field, T value, IEqualityComparer<T> equalityComparer, [CallerMemberName] string? propertyName = null)
+    {
+        ArgumentNullException.ThrowIfNull(equalityComparer);
+        if (!equalityComparer.Equals(field, value))
         {
             field = value;
             OnPropertyChanged(propertyName!);
diff --git a/src/MvvmBlazor.Tests/ViewModel/ViewModelBaseTests.cs b/src/MvvmBlazor.Tests/ViewModel/ViewModelBaseTests.cs
index eebbbfd..bbfcdcd 100644
--- a/src/MvvmBlazor.Tests/ViewModel/ViewModelBaseTests.cs
+++ b/src/MvvmBlazor.Tests/ViewModel/ViewModelBaseTests.cs
@@ -1,4 +1,4 @@
-namespace MvvmBlazor.Tests.ViewModel;
+namespace MvvmBlazor.Tests.ViewModel;
 
 public class ViewModelBaseTests
 {
@@ -76,11 +76,48 @@ void TestField<T>(ref T field, T value)
         TestField(ref double1, 2.3);
     }
 
+    [Fact]
+    public void Set_returns_False_with_custom_equality_comparer()
+    {
+        var mockEq= new StrictMock<IEqualityComparer<int>>();
+        mockEq.Setup(x => x.Equals(It.IsAny<int>(), It.IsAny<int>()))
+            .Returns(true)
+            .Verifiable();
+
+        var vm = new TestViewModel();
+        var int1 = 1;
+        var res = vm.SetProperty(ref int1, 2, mockEq.Object, "Foo");
+
+        res.ShouldBe(false);
+        mockEq.Verify();
+    }
+
+    [Fact]
+    public void Set_returns_true_with_custom_equality_comparer()
+    {
+        var mockEq= new StrictMock<IEqualityComparer<int>>();
+        mockEq.Setup(x => x.Equals(It.IsAny<int>(), It.IsAny<int>()))
+            .Returns(false)
+            .Verifiable();
+
+        var vm = new TestViewModel();
+        var int1 = 1;
+        var res = vm.SetProperty(ref int1, 1, mockEq.Object, "Foo");
+
+        res.ShouldBe(true);
+        mockEq.Verify();
+    }
+
     private class TestViewModel : ViewModelBase
     {
         public bool SetProperty<T>(ref T field, T value, string? propertyName = null)
         {
             return Set(ref field, value, propertyName);
         }
+
+        public bool SetProperty<T>(ref T field, T value, IEqualityComparer<T> equalityComparer, string? propertyName = null)
+        {
+            return Set(ref field, value, equalityComparer, propertyName);
+        }
     }
 }
\ No newline at end of file