Public Function Replace( _
   ByVal item As T _
) As Boolean

public bool Replace( 
   T item
)

MyValue one = new MyValue(1);
MyValue two = new MyValue(2);
SetList<MyValue> set = new SetList<MyValue>();
set.Add(one);
set.Add(two);

Assert.IsTrue(Object.ReferenceEquals(one, set[0]));
Assert.IsTrue(set.Replace(new MyValue(1)));
Assert.IsFalse(Object.ReferenceEquals(one, set[0]));

Assert.AreEqual(2, set.Count);
Assert.IsFalse(set.Replace(new MyValue(3))); //not replaced, then added
Assert.AreEqual(3, set.Count);

Dim one As New MyValue(1)
Dim two As New MyValue(2)
Dim [set] As New SetList(Of MyValue)()
[set].Add(one)
[set].Add(two)

Assert.IsTrue([Object].ReferenceEquals(one, [set](0)))
Assert.IsTrue([set].Replace(New MyValue(1)))
Assert.IsFalse([Object].ReferenceEquals(one, [set](0)))

Assert.AreEqual(2, [set].Count)
Assert.IsFalse([set].Replace(New MyValue(3)))
'not replaced, then added
Assert.AreEqual(3, [set].Count)