# <a id="CapyKit_PropertyComparer_2"></a> Class PropertyComparer<T, U\>

Namespace: [CapyKit](CapyKit.md)  
Assembly: CapyKit.dll  

A object comparer that can accept a lambda expression to compare properties.

```csharp
public class PropertyComparer<T, U> : IEqualityComparer<T>
```

#### Type Parameters

`T` 

Generic type parameter of the parent object.

`U` 

Generic type parameter of the property value.

#### Inheritance

[object](https://learn.microsoft.com/dotnet/api/system.object) ← 
[PropertyComparer<T, U\>](CapyKit.PropertyComparer\-2.md)

#### Implements

[IEqualityComparer<T\>](https://learn.microsoft.com/dotnet/api/system.collections.generic.iequalitycomparer\-1)

#### Inherited Members

[object.Equals\(object?\)](https://learn.microsoft.com/dotnet/api/system.object.equals\#system\-object\-equals\(system\-object\)), 
[object.Equals\(object?, object?\)](https://learn.microsoft.com/dotnet/api/system.object.equals\#system\-object\-equals\(system\-object\-system\-object\)), 
[object.GetHashCode\(\)](https://learn.microsoft.com/dotnet/api/system.object.gethashcode), 
[object.GetType\(\)](https://learn.microsoft.com/dotnet/api/system.object.gettype), 
[object.MemberwiseClone\(\)](https://learn.microsoft.com/dotnet/api/system.object.memberwiseclone), 
[object.ReferenceEquals\(object?, object?\)](https://learn.microsoft.com/dotnet/api/system.object.referenceequals), 
[object.ToString\(\)](https://learn.microsoft.com/dotnet/api/system.object.tostring)

#### Extension Methods

[ObjectExtensions.UpdateProperties<PropertyComparer<T, U\>\>\(PropertyComparer<T, U\>, PropertyComparer<T, U\>\)](CapyKit.Extensions.ObjectExtensions.md\#CapyKit\_Extensions\_ObjectExtensions\_UpdateProperties\_\_1\_\_\_0\_\_\_0\_), 
[ObjectExtensions.UpdateProperties\(object, object\)](CapyKit.Extensions.ObjectExtensions.md\#CapyKit\_Extensions\_ObjectExtensions\_UpdateProperties\_System\_Object\_System\_Object\_)

## Examples

 using System;
using System.Collections.Generic;
using System.Linq;

class Program
{
    static void Main(string[] args)
    {
        var people = new List&lt;Person&gt;
    {
        new Person { Name = "Alice", Age = 30 }, new Person { Name = "Bob", Age = 30 }, new
        Person { Name = "Charlie", Age = 35 }
    };

        var comparer = new PropertyComparer<Person, int>(p => p.Age);
        var distinctPeople = people.Distinct(comparer).ToList();

        foreach (var person in distinctPeople)
        {
            Console.WriteLine($"{person.Name} - {person.Age}");
        }
    }
}

class Person
{
    public string Name { get; set; }
    public int Age { get; set; }
}

## Constructors

### <a id="CapyKit_PropertyComparer_2__ctor_System_Func__0__1__"></a> PropertyComparer\(Func<T, U\>\)

Constructor.

```csharp
public PropertyComparer(Func<T, U> expression)
```

#### Parameters

`expression` [Func](https://learn.microsoft.com/dotnet/api/system.func\-2)<T, U\>

The expression.

## Methods

### <a id="CapyKit_PropertyComparer_2_Equals__0__0_"></a> Equals\(T, T\)

Determines whether the specified properties are equal.

```csharp
public bool Equals(T x, T y)
```

#### Parameters

`x` T

The first object of type <code class="typeparamref">T</code> to compare.

`y` T

The second object of type <code class="typeparamref">T</code> to compare.

#### Returns

 [bool](https://learn.microsoft.com/dotnet/api/system.boolean)

<a href="https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool">true</a> if the specified objects are equal; otherwise,
<a href="https://learn.microsoft.com/dotnet/csharp/language-reference/builtin-types/bool">false</a>.

### <a id="CapyKit_PropertyComparer_2_GetHashCode__0_"></a> GetHashCode\(T\)

Returns a hash code for the specified object.

```csharp
public int GetHashCode(T obj)
```

#### Parameters

`obj` T

The <xref href="System.Object" data-throw-if-not-resolved="false"></xref> for which a hash code is to be returned.

#### Returns

 [int](https://learn.microsoft.com/dotnet/api/system.int32)

A hash code for the specified object.

#### Exceptions

 [ArgumentNullException](https://learn.microsoft.com/dotnet/api/system.argumentnullexception)

The type of <code class="paramref">obj</code> is a reference type and
<code class="paramref">obj</code> is
<a href="https://learn.microsoft.com/dotnet/csharp/language-reference/keywords/null">null</a>.