String.IndexOf Method (String, Int32, StringComparison)
Reports the zero-based index of the first occurrence of the specified string in the current String object. Parameters specify the starting search position in the current string and the type of search to use for the specified string.
Assembly: mscorlib (in mscorlib.dll)
member IndexOf : value:string * startIndex:int * comparisonType:StringComparison -> int
- Type: System.String
The string to seek.
- Type: System.Int32
The search starting position.
- Type: System.StringComparison
One of the enumeration values that specifies the rules for the search.
Index numbering starts from 0. The startIndex parameter can range from 0 to the length of the string instance. If startIndex equals the length of the string instance, the method returns -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.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 startIndex, which is the character position at which the search begins.
In the following example, the method is used to find the position of a soft hyphen (U+00AD) followed by an "m" starting with the third character position in two strings. Only one of the strings contains the required substring.If the example is run on the .NET Framework 4 or later, in both cases, because the soft hyphen is an ignorable character, the method returns the index of "m" in the string when it performs a culture-sensitive comparison. Note that in the case of the first string, which includes the soft hyphen followed by an "m", the method fails to return the index of the soft hyphen but instead returns the index of the "m". The method returns the index of the soft hyphen in the first string only when it performs an ordinal comparison.