Use IEqualityComparer<TOption> instead of Func<TOption, TOption, bool>

examples/Demo/Shared/Microsoft.FluentUI.AspNetCore.Components.xml

@@ -6408,7 +6408,6 @@
         <member name="P:Microsoft.FluentUI.AspNetCore.Components.ListComponentBase`1.OptionComparer">
             <summary>
             Gets or sets the function used to determine if an option is already added to the internal list.
-            The first parameter is the item from the internal list to check and the second parameter is the actual selected item from the menu.
             </summary>
         </member>
         <member name="P:Microsoft.FluentUI.AspNetCore.Components.ListComponentBase`1.Items">

examples/Demo/Shared/Pages/List/Autocomplete/Examples/AutocompleteDifferentObjectInstances.razor

@@ -16,7 +16,7 @@
                             Class="w-100"
                             Placeholder="Name"
                             OnOptionsSearch="@OnSearchUserAsync"
-                            OptionComparer="IsOptionAdded"
+                            OptionComparer="MyComparer.Instance"
                             OptionText="@(item => $"{item.Firstname} {item.Lastname}" )"
                             @bind-SelectedOptions="Users2" />
     </div> 
@@ -26,12 +26,6 @@
     public IEnumerable<SimplePerson> Users1 { get; set; } = [new SimplePerson { Firstname = "Marvin", Lastname = "Klein", Age = 28 }];
     public IEnumerable<SimplePerson> Users2 { get; set; } = [new SimplePerson { Firstname = "Marvin", Lastname = "Klein", Age = 28 }];
 
-    private bool IsOptionAdded(SimplePerson listItem, SimplePerson selectedItem)
-    {
-        // Compare both objects with each other to determine if they are equal
-        return listItem.Firstname == selectedItem.Firstname && listItem.Lastname == selectedItem.Lastname;
-    }
-
     private Task OnSearchUserAsync(OptionsSearchEventArgs<SimplePerson> e)
     {
         // Simulate new instances for every search. Typically you would retrieve these from a database or an API.
@@ -46,4 +40,28 @@
 
         return Task.CompletedTask;
     }
+
+    public class MyComparer : IEqualityComparer<SimplePerson>
+    {
+        public static readonly MyComparer Instance = new();
+
+        public bool Equals(SimplePerson? x, SimplePerson? y)
+        {
+            if (ReferenceEquals(x, y))
+            {
+                return true;
+            }
+
+            if (x is null || y is null)
+            {
+                return false;
+            }
+
+            return x.Firstname == y.Firstname &&
+                   x.Lastname == y.Lastname &&
+                   x.Age == y.Age;
+        }
+
+        public int GetHashCode(SimplePerson obj) => HashCode.Combine(obj.Firstname, obj.Lastname, obj.Age);
+    }
 }

src/Core/Components/List/ListComponentBase.razor.cs

@@ -130,10 +130,9 @@ protected string? InternalValue
     public virtual Func<TOption, bool>? OptionSelected { get; set; }
     /// <summary>
     /// Gets or sets the function used to determine if an option is already added to the internal list.
-    /// The first parameter is the item from the internal list to check and the second parameter is the actual selected item from the menu.
     /// </summary>
     [Parameter]
-    public virtual Func<TOption, TOption, bool>? OptionComparer { get; set; }
+    public virtual IEqualityComparer<TOption>? OptionComparer { get; set; }
 
     /// <summary>
     /// Gets or sets the content source of all items to display in this list.
@@ -544,7 +543,7 @@ protected virtual async Task OnSelectedItemChangedHandlerAsync(TOption? item)
                 RemoveSelectedItem(item);
                 await RaiseChangedEventsAsync();
             }
-            else if (OptionComparer is not null && _selectedOptions.FirstOrDefault(x => OptionComparer(x, item)) is TOption addedItem)
+            else if (OptionComparer is not null && _selectedOptions.FirstOrDefault(x => OptionComparer.Equals(x, item)) is TOption addedItem)
             {
                 RemoveSelectedItem(addedItem);
                 await RaiseChangedEventsAsync();

tests/Core/List/FluentAutocompleteTests.razor

@@ -504,7 +504,7 @@
         var cut = Render<FluentAutocomplete<Customer>>(
             @<FluentAutocomplete TOption="Customer"
                     SelectValueOnTab="true"
-                    OptionComparer="IsItemAdded"
+                    OptionComparer="CustomerComparer.Instance"
                     @bind-SelectedOptions="@SelectedItems"
                     OnOptionsSearch="@OnSearchNewInstance" />
             );
@@ -551,8 +551,26 @@
         return Task.CompletedTask;
     }
 
-    private bool IsItemAdded(Customer listItem, Customer selectedItem)
+    public class CustomerComparer : IEqualityComparer<Customer>
     {
-        return listItem.Id == selectedItem.Id;
+        public static readonly CustomerComparer Instance = new();
+
+        public bool Equals(Customer? x, Customer? y)
+        {
+            if (ReferenceEquals(x, y))
+            {
+                return true;
+            }
+
+            if (x is null || y is null)
+            {
+                return false;
+            }
+
+            return x.Id == y.Id &&
+                   x.Name == y.Name;
+        }
+
+        public int GetHashCode(Customer obj) => HashCode.Combine(obj.Id, obj.Name);
     }
 }