Reading the result

TextDiff.ComputeDiff returns a TextDiffResult:

• HasDifferences is true when the texts differ under the comparison options that were used. Two texts that differ only in casing have no differences with IgnoreCase.
• Entries holds the chunks of both texts, in order. Each TextDiffEntry has an Operation (Equal, Delete or Insert) and the text of the chunk.
• ToString() counts the entries of each operation, which is handy in logs.

The order of the entries

The entries follow both texts from start to end. Between two Equal entries, the deleted chunks come first, then the inserted chunks: a changed line is a Delete entry followed by an Insert entry, never the other way around.

The text of an entry

An entry has three text properties:

Text is never null, which makes it the simplest property to display. Without comparison options, the two sides of an Equal entry are the same string. With IgnoreCase or IgnoreWhitespace, two different chunks can compare equal: OldText and NewText then differ, and Text is the chunk of the old text.

Rebuild either text

Concatenate OldText for the Equal and Delete entries to get the old text, and NewText for the Equal and Insert entries to get the new text. This works whatever the comparison options:

var result = TextDiff.ComputeDiff("Hello\nWorld\n", "hello\nWORLD\nagain\n", new TextDiffOptions { IgnoreCase = true });

var oldText = string.Concat(result.Entries
    .Where(e => e.Operation is TextDiffOperation.Equal or TextDiffOperation.Delete)
    .Select(e => e.OldText));

var newText = string.Concat(result.Entries
    .Where(e => e.Operation is TextDiffOperation.Equal or TextDiffOperation.Insert)
    .Select(e => e.NewText));

Assert.Equal("Hello\nWorld\n", oldText);
Assert.Equal("hello\nWORLD\nagain\n", newText);

The texts are rebuilt exactly because the built-in chunkers keep every character, line terminators included. A custom chunker must do the same. IgnoreEndOfLine is the exception: it normalizes the line terminators before the texts are split, so the entries hold \n instead of the original terminators. See Comparison options.

Compare entries

TextDiffEntry is a value type with value equality: two entries are equal when they have the same operation, the same OldText and the same NewText. This is what lets the examples of this documentation compare Entries with a list of expected entries, created with the TextDiffEntry(operation, text) constructor.