WildcardPattern

WildcardPattern.Escape() does not escape some backticks

The escape character of WildcardPattern is backtick. It looks like if an input string contains backticks which are not followed by characters []?* then WildcardPattern.Escape() keeps them intact instead of escaping each backtick with a backtick.

Compare with Regex. The escape character is backslash. If an input string contains backslashes then Regex.Escape() escapes each backslash with a backslash.

By design an escaped string as a pattern should match the original string. This is not always the case with WildcardPattern. If a string contains backticks then its escaped pattern may not match the original string. Also, the method WildcardPattern.UnEscape() applied to an escaped string may not produce the original string.

Workaround

One possible workaround is to escape a string using this regular expression:

    $escaped = $string -replace '([`*?[\]])', '`$1'

As a result, an escaped string matches the original with the operator -like and the method WildcardPattern.UnEscape() gets the original string.

Scripts

• Test-1-Escape-UnEscape-wildcard.ps1 shows that WildcardPattern.Escape() produces a pattern not matching the original string and UnEscape() does not get the original string.
• Test-2-Escape-UnEscape-regex.ps1 shows how Regex.Escape() works in the similar case (backslashes instead of backticks).
• Test-3-Escape-workaround.ps1 tests the workaround.

---

• Microsoft Connect 336327