String.LastIndexOf Method (String, StringComparison)

Reports the zero-based index of the last occurrence of a specified string within the current String object. A parameter specifies the type of search to use for the specified string.

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

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

Parameters

value
Type: System.String

The string to seek.

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. If value is String.Empty, the return value is the last index position in this instance.

ExceptionCondition
ArgumentNullException

value is a null reference (Nothing in Visual Basic).

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 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.

The search begins at the last character position of this instance and proceeds backward toward the beginning until either value is found or the first character position has been examined.

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 options 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 method always returns String.Length – 1, which represents the last index position in the current instance.

In the following example, the LastIndexOf(String, StringComparison) 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.

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

The following example demonstrates 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.

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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