String extensions¶

Helpers for common string manipulation tasks: filtering characters, extracting head/tail segments, trimming from either end, and rendering strings as hexadecimal. All methods are extension methods on string and return new strings (do not mutate the original).

See also - ASCII Mnemonic Expansion — show control characters as mnemonics (e.g., \<CR>)

Clean: remove unwanted characters¶

Removes all characters that appear in the supplied clean set and preserves the rest.

var source = "A-B_C";
var cleaned = source.Clean("-_");   // "ABC"

Notes - If source is null or empty, returns string.Empty. - If clean is null or empty, returns source unchanged. - Complexity is O(n × m) where n is the source length and m is clean.Length. A HashSet can be faster when clean is very large, but for typical small sets the simple approach is competitive.

Keep: keep only wanted characters¶

The inverse of Clean. Keeps only characters that appear in the supplied keep set and removes all others.

var digits = "a1b2c3".Keep("0123456789"); // "123"

Notes - If source is null or empty, returns string.Empty.

Head: take the first N characters¶

Returns the first length characters of the string.

"abcdef".Head(3);     // "abc"

Exceptions - ArgumentNullException if source is null. - ArgumentOutOfRangeException if length < 0 or length > source.Length.

Tail: take the last N characters¶

Returns the last length characters of the string.

"abcdef".Tail(2);     // "ef"

Exceptions - ArgumentOutOfRangeException if length > source.Length.

RemoveHead: drop N characters from the start¶

Removes length characters from the start; returns the remainder.

"abcdef".RemoveHead(2);   // "cdef"

Notes - If length < 1, returns source unchanged. - If length exceeds the source length, Tail() will throw; ensure the value is within range if you do not want an exception.

RemoveTail: drop N characters from the end¶

Removes length characters from the end; returns the remainder.

"abcdef".RemoveTail(2);   // "abcd"

Notes - If length < 1, returns source unchanged. - If length exceeds the source length, Head() will throw; ensure the value is within range if you do not want an exception.

ToHex: visualise character codes¶

Renders each character’s numeric value in lower‑case hexadecimal, surrounded by braces.

"Az".ToHex();   // "{41, 7a}"

Notes - Useful for diagnostics and debugger output when inspecting non‑printable characters or code points.

There is a companion set of helpers for splitting a string or stream into lines without allocating the entire array up front.

// From a string
foreach (var line in bigText.GetLines()) { /* ... */ }

// From a stream
await using var fs = File.OpenRead(path);
foreach (var line in fs.GetLines()) { /* ... */ }

Rules - A line ends at CR (0x0D), LF (0x0A), CRLF, Environment.NewLine, or end‑of‑input; terminators are not included in the returned lines.