String.LastIndexOf Method (String, Int32, Int32)
Reports the zero-based index position of the last occurrence of a specified string within this instance. The search starts at a specified character position and proceeds backward toward the beginning of the string for a specified number of character positions.
Assembly: mscorlib (in mscorlib.dll)
- Type: System.String
The string to seek.
- Type: System.Int32
The search starting position. The search proceeds from startIndex toward the beginning of this instance.
- Type: System.Int32
The number of character positions to examine.
value is a null reference (Nothing in Visual Basic).
count is negative.
The current instance does not equal String.Empty, and startIndex is negative.
The current instance does not equal String.Empty, and startIndex is greater than the length of this instance.
The current instance does not equal String.Empty, and startIndex - count + 1 specifies a position that is not within this instance.
The current instance equals String.Empty and start is less than -1 or greater than zero.
The current instance equals String.Empty and count is greater than 1.
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 search begins at the startIndex character position of this instance and proceeds backward toward the beginning until either value is found or count character positions have been examined. For example, if startIndex is Length - 1, the method searches backward count characters from the last character in the string.
This method performs a word (case-sensitive and culture-sensitive) search using the current culture.
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, 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 startIndex, which is the character position at which the search begins. In the following example, the LastIndexOf method is used to find the position of a soft hyphen (U+00AD) in the two characters that precede the final "m" of 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".Notes to Callers
As explained in Best Practices for Using Strings in the .NET Framework, we recommend that you avoid calling string comparison methods that substitute default values and instead call methods that require parameters to be explicitly specified. To perform this operation by using the comparison rules of the current culture, call the LastIndexOf(String, Int32, Int32, StringComparison) method overload with a value of StringComparison.CurrentCulture for its comparisonType parameter.