String.LastIndexOf Method (String, StringComparison)
Reports the zero-based index of the last occurrence of a specified string within the current String object. A parameter specifies the type of search to use for the specified string.
Assembly: mscorlib (in mscorlib.dll)
- Type: System.String
The string to seek.
- Type: System.StringComparison
One of the enumeration values that specifies the rules for the search.
Index numbering starts from zero. That is, the first character in the string is at index zero and the last is at Length - 1.
The comparisonType parameter specifies to search for the value parameter using the current or invariant culture, using a case-sensitive or case-insensitive search, and using word or ordinal comparison rules.
The search begins at the last character position of this instance and proceeds backward toward the beginning until either value is found or the first character position has been examined.Notes to Callers
Character sets include ignorable characters, which are characters that are not considered when performing a linguistic or culture-sensitive comparison. In a culture-sensitive search (that is, if options is not StringComparison.Ordinal or StringComparison.OrdinalIgnoreCase), if value contains an ignorable character, the result is equivalent to searching with that character removed. If value consists only of one or more ignorable characters, the LastIndexOf method always returns String.Length – 1, which represents the last index position in the current instance.
In the following example, the method is used to find three substrings (a soft hyphen (U+00AD), a soft hyphen followed by "n", and a soft hyphen followed by "m") in two strings. Only one of the strings contains a soft hyphen. If the example is run on the .NET Framework 4 or later, because the soft hyphen is an ignorable character, a culture-sensitive search returns the same value that it would return if the soft hyphen were not included in the search string. An ordinal search, however, successfully finds the soft hyphen in one string and reports that it is absent from the second string.