String.IndexOf Method (String, StringComparison)
Reports the zero-based index of the first occurrence of the specified string in 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.
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.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 comparisonType 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 method always returns 0 (zero) to indicate that the match is found at the beginning of 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.