/// <summary>
/// Returns an equality comparer that uses a key comparer if the source comparer determines the objects are equal.
/// </summary>
/// <typeparam name="T">The type of objects being compared.</typeparam>
/// <typeparam name="TKey">The type of key objects being compared.</typeparam>
/// <param name="source">The source comparer. If this is <c>null</c>, the default comparer is used.</param>
/// <param name="selector">The key selector. May not be <c>null</c>.</param>
/// <param name="comparerFactory">The definition of the key comparer. May not be <c>null</c>.</param>
/// <param name="specialNullHandling">A value indicating whether <c>null</c> values are passed to <paramref name="selector"/>. If <c>false</c>, then <c>null</c> values are considered less than any non-<c>null</c> values and are not passed to <paramref name="selector"/>. This value is ignored if <typeparamref name="T"/> is a non-nullable type.</param>
/// <returns>A comparer that uses a key comparer if the source comparer determines the objects are equal.</returns>
public static IFullEqualityComparer <T> ThenEquateBy <T, TKey>(this IEqualityComparer <T>?source, Func <T, TKey> selector, Func <EqualityComparerBuilderFor <TKey>, IEqualityComparer <TKey> > comparerFactory, bool specialNullHandling = false)
{
_ = comparerFactory ?? throw new ArgumentNullException(nameof(comparerFactory));
var comparer = comparerFactory(EqualityComparerBuilder.For <TKey>());
return(source.ThenEquateBy(selector, comparer, specialNullHandling));
}
public void SubstitutesCompareDefaultForNull()
{
IEqualityComparer <Person> thenByComparer = EqualityComparerBuilder.For <Person>().EquateBy(p => p.FirstName);
IEqualityComparer <Person> source = null;
var comparer = source.ThenEquateBy(thenByComparer);
Assert.Equal(EqualityComparerBuilder.For <Person>().Default().ThenEquateBy(thenByComparer).ToString(), comparer.ToString());
}
public void SubstitutesCompareDefaultForNull()
{
IEqualityComparer <Person> thenByComparer = EqualityCompare <string> .Default().SelectEquateFrom((Person p) => p.FirstName);
IEqualityComparer <Person> source = null;
var comparer = source.ThenEquateBy(thenByComparer);
Assert.AreSame(EqualityCompare <Person> .Default(), (comparer as CompoundEqualityComparer <Person>).Source);
}
public void ThenByIsAppliedAsTieBreaker()
{
IEqualityComparer <Person> thenByComparer = EqualityComparerBuilder.For <Person>().EquateBy(p => p.FirstName);
IEqualityComparer <Person> defaultComparer = EqualityComparerBuilder.For <Person>().Default();
IEqualityComparer <Person> fullComparer = defaultComparer.ThenEquateBy(thenByComparer);
Assert.True(defaultComparer.Equals(AbeAbrams, WilliamAbrams));
Assert.Equal(defaultComparer.GetHashCode(AbeAbrams), defaultComparer.GetHashCode(WilliamAbrams));
Assert.False(thenByComparer.Equals(AbeAbrams, WilliamAbrams));
Assert.False(fullComparer.Equals(AbeAbrams, WilliamAbrams));
}
public void ThenByIsAppliedAsTieBreaker()
{
IEqualityComparer <Person> thenByComparer = EqualityCompare <string> .Default().SelectEquateFrom((Person p) => p.FirstName);
IEqualityComparer <Person> defaultComparer = EqualityCompare <Person> .Default();
IEqualityComparer <Person> fullComparer = defaultComparer.ThenEquateBy(thenByComparer);
Assert.IsTrue(defaultComparer.Equals(AbeAbrams, WilliamAbrams));
Assert.AreEqual(defaultComparer.GetHashCode(AbeAbrams), defaultComparer.GetHashCode(WilliamAbrams));
Assert.IsFalse(thenByComparer.Equals(AbeAbrams, WilliamAbrams));
Assert.IsFalse(fullComparer.Equals(AbeAbrams, WilliamAbrams));
}
/// <summary>
/// Returns an equality comparer that uses a key comparer if the source comparer determines the objects are equal.
/// </summary>
/// <typeparam name="T">The type of objects being compared.</typeparam>
/// <typeparam name="TKey">The type of key objects being compared.</typeparam>
/// <param name="source">The source comparer. If this is <c>null</c>, the default comparer is used.</param>
/// <param name="selector">The key selector. May not be <c>null</c>.</param>
/// <param name="keyComparer">The key comparer. Defaults to <c>null</c>. If this is <c>null</c>, the default comparer is used.</param>
/// <param name="allowNulls">A value indicating whether <c>null</c> values are passed to <paramref name="selector"/>. If <c>false</c>, then <c>null</c> values are considered less than any non-<c>null</c> values and are not passed to <paramref name="selector"/>.</param>
/// <returns>A comparer that uses a key comparer if the source comparer determines the objects are equal.</returns>
public static IEqualityComparer <T> ThenEquateBy <T, TKey>(this IEqualityComparer <T> source, Func <T, TKey> selector, IEqualityComparer <TKey> keyComparer = null, bool allowNulls = false)
{
Contract.Requires(selector != null);
Contract.Ensures(Contract.Result <IEqualityComparer <T> >() != null);
return(source.ThenEquateBy(keyComparer.SelectEquateFrom(selector, allowNulls)));
}
/// <summary>
/// Returns an equality comparer that uses a key comparer if the source comparer determines the objects are equal.
/// </summary>
/// <typeparam name="T">The type of objects being compared.</typeparam>
/// <typeparam name="TKey">The type of key objects being compared.</typeparam>
/// <param name="source">The source comparer. If this is <c>null</c>, the default comparer is used.</param>
/// <param name="selector">The key selector. May not be <c>null</c>.</param>
/// <param name="keyComparer">The key comparer. Defaults to <c>null</c>. If this is <c>null</c>, the default comparer is used.</param>
/// <param name="specialNullHandling">A value indicating whether <c>null</c> values are passed to <paramref name="selector"/>. If <c>false</c>, then <c>null</c> values are considered less than any non-<c>null</c> values and are not passed to <paramref name="selector"/>. This value is ignored if <typeparamref name="T"/> is a non-nullable type.</param>
/// <returns>A comparer that uses a key comparer if the source comparer determines the objects are equal.</returns>
public static IFullEqualityComparer <T> ThenEquateBy <T, TKey>(this IEqualityComparer <T>?source, Func <T, TKey> selector, IEqualityComparer <TKey>?keyComparer = null, bool specialNullHandling = false)
{
var selectComparer = new SelectEqualityComparer <T, TKey>(selector, keyComparer, specialNullHandling);
return(source.ThenEquateBy(selectComparer));
}
/// <summary>
/// Returns an equality comparer that uses a key comparer if the source comparer determines the objects are equal.
/// </summary>
/// <typeparam name="T">The type of objects being compared.</typeparam>
/// <typeparam name="TKey">The type of key objects being compared.</typeparam>
/// <param name="source">The source comparer. If this is <c>null</c>, the default comparer is used.</param>
/// <param name="selector">The key selector. May not be <c>null</c>.</param>
/// <param name="comparerFactory">The definition of the key comparer. May not be <c>null</c>.</param>
/// <param name="specialNullHandling">A value indicating whether <c>null</c> values are passed to <paramref name="selector"/>. If <c>false</c>, then <c>null</c> values are considered less than any non-<c>null</c> values and are not passed to <paramref name="selector"/>. This value is ignored if <typeparamref name="T"/> is a non-nullable type.</param>
/// <returns>A comparer that uses a key comparer if the source comparer determines the objects are equal.</returns>
public static IFullEqualityComparer <T> ThenEquateBy <T, TKey>(this IEqualityComparer <T> source, Func <T, TKey> selector, Func <EqualityComparerBuilderFor <TKey>, IEqualityComparer <TKey> > comparerFactory, bool specialNullHandling = false)
{
var comparer = comparerFactory(EqualityComparerBuilder.For <TKey>());
return(source.ThenEquateBy(selector, comparer, specialNullHandling));
}
/// <summary>
/// Returns an equality comparer that uses a key comparer if the source comparer determines the objects are equal.
/// </summary>
/// <typeparam name="T">The type of objects being compared.</typeparam>
/// <typeparam name="TKey">The type of key objects being compared.</typeparam>
/// <param name="source">The source comparer. If this is <c>null</c>, the default comparer is used.</param>
/// <param name="selector">The key selector. May not be <c>null</c>.</param>
/// <param name="keyComparer">The key comparer. Defaults to <c>null</c>. If this is <c>null</c>, the default comparer is used.</param>
/// <param name="specialNullHandling">A value indicating whether <c>null</c> values are passed to <paramref name="selector"/>. If <c>false</c>, then <c>null</c> values are considered less than any non-<c>null</c> values and are not passed to <paramref name="selector"/>.</param>
/// <returns>A comparer that uses a key comparer if the source comparer determines the objects are equal.</returns>
public static IFullEqualityComparer <T> ThenEquateBy <T, TKey>(this IEqualityComparer <T> source, Func <T, TKey> selector, IEqualityComparer <TKey> keyComparer = null, bool specialNullHandling = false)
{
return(source.ThenEquateBy(keyComparer.SelectEquateFrom(selector, specialNullHandling)));
}
