Reports the zero-based index position of the last occurrence of the specified Unicode character in a substring 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.
The zero-based index position of value if that character is found, or -1 if it is not found or if the current instance equals string.Empty.
Type Reason ArgumentNullException value is a null reference. ArgumentOutOfRangeException
startIndex or count is less than zero.
startIndex - count is less than -1.
Index numbering starts from zero. That is, the first character in the string is at index zero and the last is at string.Length - 1.
This method begins searching at the startIndex character position and proceeds backward toward the beginning of this instance until either value is found or count character positions have been examined. For example, if startIndex is string.Length - 1, the method searches backward count characters from the last character in the string. The search is case-sensitive.
This method performs an ordinal (culture-insensitive) search, where a character is considered equivalent to another character only if their Unicode scalar value are the same. To perform a culture-sensitive search, use the System.Globalization.CompareInfo.LastIndexOf(string, char) method, where a Unicode scalar value representing a precomposed character, such as the ligature "Æ" (U+00C6), might be considered equivalent to any occurrence of the character's components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture.