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copied!<p>Since a linked list isn't a dictionary, I would <em>expect</em> it to use <code>EqualityComparer<T>.Default.Equals(x,y)</code>.</p> <p>This supports (in order):</p> <ul> <li><code>IEquatable<T></code> (for the <code>T</code> in question)</li> <li><code>object.Equals</code> (which uses reference equality by default, or supports an overridden <code>Equals(object)</code>)</li> </ul> <p>Note that <code>EqualityComparer<T></code> also handles the usual <code>null</code> rules etc for both classes and <code>Nullable<T></code>.</p> <p>(update: checked, and correct; from <code>Find(T)</code>)</p> <pre><code>... EqualityComparer<T> comparer = EqualityComparer<T>.Default; ... if (comparer.Equals(head.item, value)) {...} ... </code></pre> <hr> <p>Update to prove this working when <code>ISomeInterface: IEquatable<ISomeInterface></code>, as per comments:</p> <pre><code>using System; using System.Collections.Generic; class Program { static void Main() { LinkedList<IFoo> foos = new LinkedList<IFoo>(); foos.AddLast(new Foo1("abc")); foos.AddLast(new Foo2("def")); Console.WriteLine("checking contains..."); bool c = foos.Contains(new Foo1("ghi")); Console.WriteLine("...done"); } } interface IFoo : IEquatable<IFoo> { void Bar(); } class Foo1 : IFoo { public string Value { get; set; } public Foo1(string value) { Value = value; } public override bool Equals(object other) { Console.WriteLine(Value + " > override Equals"); return base.Equals(other); } bool IEquatable<IFoo>.Equals(IFoo other) { Console.WriteLine(Value + " > explicit Equals"); return base.Equals(other); } public void Bar() { } public override int GetHashCode() { return base.GetHashCode(); } } class Foo2 : IFoo { public string Value { get; set; } public Foo2(string value) { Value = value; } public override bool Equals(object other) { Console.WriteLine(Value + " > override Equals"); return base.Equals(other); } public bool Equals(IFoo other) { Console.WriteLine(Value + " > implicit Equals"); return base.Equals(other); } public void Bar() { } public override int GetHashCode() { return base.GetHashCode(); } } </code></pre>

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