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String.LastIndexOf Method (String, Int32, StringComparison)

 

Reports the zero-based index of the last occurrence of a specified string within the current String object. The search starts at a specified character position and proceeds backward toward the beginning of the string. A parameter specifies the type of comparison to perform when searching for the specified string.

Namespace:   System
Assembly:  mscorlib (in mscorlib.dll)

member LastIndexOf : 
        value:string *
        startIndex:int *
        comparisonType:StringComparison -> int

Parameters

value
Type: System.String

The string to seek.

startIndex
Type: System.Int32

The search starting position. The search proceeds from startIndex toward the beginning of this instance.

comparisonType
Type: System.StringComparison

One of the enumeration values that specifies the rules for the search.

Return Value

Type: System.Int32

The zero-based starting index position of the value parameter if that string is found, or -1 if it is not found or if the current instance equals String.Empty. If value is String.Empty, the return value is the smaller of startIndex and the last index position in this instance.

Exception Condition
ArgumentNullException

value is null.

ArgumentOutOfRangeException

The current instance does not equal String.Empty, and startIndex is less than zero or greater than the length of the current instance.

-or-

The current instance equals String.Empty, and startIndex is less than -1 or greater than zero.

ArgumentException

comparisonType is not a valid System.StringComparison value.

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 and proceeds backward until either value is found or the first character position has been examined. For example, if startIndex is Length - 1, the method searches every character from the last character in the string to the beginning.

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 LastIndexOf(String, Int32, StringComparison) method always returns startIndex, which is the character position at which the search begins.

In the following example, the LastIndexOf(String, Int32, StringComparison) method is used to find the position of a soft hyphen (U+00AD) followed by an "m", starting with the final "m" 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.

No code example is currently available or this language may not be supported.

The following exampledemonstrates three overloads of the LastIndexOf method that find the last occurrence of a string within another string using different values of the StringComparison enumeration.

No code example is currently available or this language may not be supported.

Universal Windows Platform
Available since 8
.NET Framework
Available since 2.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1
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