LineComparer

LineComparer.Default is the default IEqualityComparer<ILine> comparer.

IEqualityComparer<ILine> comparer = LineComparer.Default;

Table of comparers:

Comparer	Description
LineComparer.Default	Makes key comparisons
LineComparer.IgnoreCulture	Key comparer but ignores "Culture" parameters
LineComparer.KeyValue	Key and String-value comparison.
LineComparer.Parameter	Compares parameters in order of occurance.

LineComparer.Default compares parts that implement ILineCanonicalKey or ILineNonCanonicalKey, and also ILineParameter if the ParameterName recognized as key.

ILine key = LineAppender.NonResolving.Culture("en").Key("OK");
int hash = LineComparer.Default.GetHashCode(key);

Keys that are constructed from different roots are reference comparable.

ILine key1 = new LineRoot().Key("OK");
ILine key2 = LineAppender.NonResolving.Key("OK");
ILine key3 = LineRoot.Global.Key("OK");
ILine key4 = StringLocalizerRoot.Global.Key("OK");

bool equals12 = LineComparer.Default.Equals(key1, key2); // Are equal
bool equals23 = LineComparer.Default.Equals(key2, key3); // Are equal
bool equals34 = LineComparer.Default.Equals(key3, key4); // Are equal
int hash1 = LineComparer.Default.GetHashCode(key1);
int hash2 = LineComparer.Default.GetHashCode(key2);
int hash3 = LineComparer.Default.GetHashCode(key3);
int hash4 = LineComparer.Default.GetHashCode(key4);

The location of ILineNonCanonicalKey parts, such as .Culture() does not matter to the comparer.

ILine key1 = LineAppender.NonResolving.Culture("en").Key("OK");
ILine key2 = LineAppender.NonResolving.Key("OK").Culture("en");

bool equals12 = LineComparer.Default.Equals(key1, key2); // Are equal

If a non-canonical part occurs multiple times in a key, then by rule, only the left-most if considered effective.

ILine key1 = LineAppender.NonResolving.Culture("en").Key("OK");
ILine key2 = LineAppender.NonResolving.Culture("en").Key("OK").Culture("de");

bool equals12 = LineComparer.Default.Equals(key1, key2); // Are equal

A non-canonical parameter with empty value "" is considered same as not existing.

ILine key1 = LineAppender.NonResolving.Key("OK");
ILine key2 = LineAppender.NonResolving.Key("OK").Culture("");

bool equals12 = LineComparer.Default.Equals(key1, key2); // Are equal
int hash1 = LineComparer.Default.GetHashCode(key1);
int hash2 = LineComparer.Default.GetHashCode(key2);

There is a difference though, for a non-canonical parameter such as "Culture" cannot be re-selected.

ILine key1 = LineAppender.NonResolving.Key("OK").Culture("fi"); // <- Selects a culture
ILine key2 = LineAppender.NonResolving.Key("OK").Culture("").Culture("fi"); // <- Culture "" remains
string str1 = LineFormat.Line.Print(key1);
string str2 = LineFormat.Line.Print(key2);

A canonical parameter with empty value "" is considered meaningful for hash-equals comparison.

ILine key1 = LineAppender.NonResolving.Section("").Key("OK");
ILine key2 = LineAppender.NonResolving.Key("OK");

bool equals12 = LineComparer.Default.Equals(key1, key2); // Are not equal
int hash1 = LineComparer.Default.GetHashCode(key1);
int hash2 = LineComparer.Default.GetHashCode(key2);