/// <summary>
/// Returns a new instance of <see cref="IEqualityComparer{T}"/> using the given implementation of <see cref="IEquatable{T}"/>.
/// </summary>
/// <typeparam name="T">The type of the objects to compare.</typeparam>
/// <returns>A new instance of <see cref="IEqualityComparer{T}"/>.</returns>
public static IEqualityComparer <T> FromIEquatable <T>()
where T : IEquatable <T>
{
Type type = typeof(T);
Object syncRoot = (_cache as ICollection).SyncRoot;
IEqualityComparer <T> comparer = null;
lock (syncRoot) {
if (_cache.ContainsKey(type))
{
comparer = _cache[type] as IEqualityComparer <T>;
}
}
if (comparer == null)
{
EqualityComparison <T> equals = (x, y) => {
if (x == null && y == null)
{
return(true);
}
if (x != null && y != null)
{
return(x.Equals(y));
}
return(false);
};
comparer = new InternalEqualityComparer <T>(equals, (obj) => obj.GetHashCode());
lock (syncRoot) {
if (!_cache.ContainsKey(type))
{
_cache.Add(type, comparer);
}
}
}
return(comparer);
}
void Ctor()
{
IEqualityComparer comp = null;
Boolean result = false;
Int32 hash = 0;
Test.If.Action.ThrowsException(() => comp = new InternalEqualityComparer(null, null), out ArgumentNullException ex1);
Test.If.Value.IsEqual(ex1.ParamName, "equals");
Test.If.Action.ThrowsException(() => comp = new InternalEqualityComparer(null, (obj) => 42), out ex1);
Test.If.Value.IsEqual(ex1.ParamName, "equals");
Test.If.Action.ThrowsException(() => comp = new InternalEqualityComparer((x, y) => true, null), out ex1);
Test.If.Value.IsEqual(ex1.ParamName, "getHashCode");
Test.IfNot.Action.ThrowsException(() => comp = new InternalEqualityComparer((x, y) => true, (obj) => 42), out Exception ex2);
result = comp.Equals(0, 1);
Test.If.Value.IsEqual(result, true);
hash = comp.GetHashCode(0);
Test.If.Value.IsEqual(hash, 42);
}