CompareInfo.LastIndexOf Method (String, Char, CompareOptions)
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Searches for the specified character and returns the zero-based index of the last occurrence within the entire source string using the specified CompareOptions value.
Assembly: mscorlib (in mscorlib.dll)
Parameters
- source
- Type: System.String
The string to search.
- value
- Type: System.Char
The character to locate within source.
- options
- Type: System.Globalization.CompareOptions
The CompareOptions value that defines how source and value should be compared. options is either the value Ordinal used by itself, or the bitwise combination of one or more of the following values: IgnoreCase, IgnoreSymbols, IgnoreNonSpace, IgnoreWidth, and IgnoreKanaType.
Return Value
Type: System.Int32The zero-based index of the last occurrence of value within the entire source using the specified CompareOptions value, if found; otherwise, -1.
| Exception | Condition |
|---|---|
| ArgumentNullException | source is null. |
| ArgumentException | options contains an invalid CompareOptions value. |
The source string is searched backward starting at the end of the string and ending at the beginning of the string.
The CompareOptions.StringSort value is not valid for this method.
If options does not include the Ordinal value, this overload performs a culture-sensitive search. If the character is a Unicode value representing a precomposed character, such as the ligature "Æ" (U+00C6), it might be considered equivalent to any occurrence of its components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture. If options includes the Ordinal value, this overload performs an ordinal (culture-insensitive) search. A character is considered equivalent to another character only if the Unicode values are the same.
The following example determines the indexes of the first and last occurrences of a character or a substring within a string.
using System; using System.Globalization; public class Example { public static void Demo(System.Windows.Controls.TextBlock outputBlock) { // Creates CompareInfo for the InvariantCulture. CompareInfo myComp = CultureInfo.InvariantCulture.CompareInfo; // Searches for the ligature Æ. String myStr = "Is AE or ae the same as Æ or æ?"; outputBlock.Text += "\n"; outputBlock.Text += String.Format("No options : {0}", myStr) + "\n"; PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE"), myComp.LastIndexOf(myStr, "AE")); PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae"), myComp.LastIndexOf(myStr, "ae")); PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, 'Æ'), myComp.LastIndexOf(myStr, 'Æ')); PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, 'æ'), myComp.LastIndexOf(myStr, 'æ')); outputBlock.Text += String.Format("Ordinal : {0}", myStr) + "\n"; PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE", CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "AE", CompareOptions.Ordinal)); PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae", CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "ae", CompareOptions.Ordinal)); PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, 'Æ', CompareOptions.Ordinal), myComp.LastIndexOf(myStr, 'Æ', CompareOptions.Ordinal)); PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, 'æ', CompareOptions.Ordinal), myComp.LastIndexOf(myStr, 'æ', CompareOptions.Ordinal)); outputBlock.Text += String.Format("IgnoreCase : {0}", myStr) + "\n"; PrintMarker(outputBlock, " AE : ", myComp.IndexOf(myStr, "AE", CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "AE", CompareOptions.IgnoreCase)); PrintMarker(outputBlock, " ae : ", myComp.IndexOf(myStr, "ae", CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "ae", CompareOptions.IgnoreCase)); PrintMarker(outputBlock, " Æ : ", myComp.IndexOf(myStr, 'Æ', CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, 'Æ', CompareOptions.IgnoreCase)); PrintMarker(outputBlock, " æ : ", myComp.IndexOf(myStr, 'æ', CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, 'æ', CompareOptions.IgnoreCase)); // Searches for the combining character sequence Latin capital letter U with diaeresis or Latin small letter u with diaeresis. myStr = "Is \u0055\u0308 or \u0075\u0308 the same as \u00DC or \u00FC?"; outputBlock.Text += "\n"; outputBlock.Text += String.Format("No options : {0}", myStr) + "\n"; PrintMarker(outputBlock, " U\u0308 : ", myComp.IndexOf(myStr, "U\u0308"), myComp.LastIndexOf(myStr, "U\u0308")); PrintMarker(outputBlock, " u\u0308 : ", myComp.IndexOf(myStr, "u\u0308"), myComp.LastIndexOf(myStr, "u\u0308")); PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, 'Ü'), myComp.LastIndexOf(myStr, 'Ü')); PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, 'ü'), myComp.LastIndexOf(myStr, 'ü')); outputBlock.Text += String.Format("Ordinal : {0}", myStr) + "\n"; PrintMarker(outputBlock, " U\u0308 : ", myComp.IndexOf(myStr, "U\u0308", CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "U\u0308", CompareOptions.Ordinal)); PrintMarker(outputBlock, " u\u0308 : ", myComp.IndexOf(myStr, "u\u0308", CompareOptions.Ordinal), myComp.LastIndexOf(myStr, "u\u0308", CompareOptions.Ordinal)); PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, 'Ü', CompareOptions.Ordinal), myComp.LastIndexOf(myStr, 'Ü', CompareOptions.Ordinal)); PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, 'ü', CompareOptions.Ordinal), myComp.LastIndexOf(myStr, 'ü', CompareOptions.Ordinal)); outputBlock.Text += String.Format("IgnoreCase : {0}", myStr) + "\n"; PrintMarker(outputBlock, " U\u0308 : ", myComp.IndexOf(myStr, "U\u0308", CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "U\u0308", CompareOptions.IgnoreCase)); PrintMarker(outputBlock, " u\u0308 : ", myComp.IndexOf(myStr, "u\u0308", CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, "u\u0308", CompareOptions.IgnoreCase)); PrintMarker(outputBlock, " Ü : ", myComp.IndexOf(myStr, 'Ü', CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, 'Ü', CompareOptions.IgnoreCase)); PrintMarker(outputBlock, " ü : ", myComp.IndexOf(myStr, 'ü', CompareOptions.IgnoreCase), myComp.LastIndexOf(myStr, 'ü', CompareOptions.IgnoreCase)); } public static void PrintMarker(System.Windows.Controls.TextBlock outputBlock, String Prefix, int First, int Last) { // Determines the size of the array to create. int mySize; if (Last > First) mySize = Last; else mySize = First; if (mySize > -1) { // Creates an array of Char to hold the markers. Char[] myCharArr = new Char[mySize + 1]; // Inserts the appropriate markers. if (First > -1) myCharArr[First] = 'f'; if (Last > -1) myCharArr[Last] = 'l'; if (First == Last) myCharArr[First] = 'b'; // Displays the array of Char as a String. outputBlock.Text += String.Format("{0}{1}", Prefix, new String(myCharArr)) + "\n"; } else outputBlock.Text += Prefix + "\n"; } } /* This code produces the following output. No options : Is AE or ae the same as Æ or æ? AE : f l ae : f l Æ : f l æ : f l Ordinal : Is AE or ae the same as Æ or æ? AE : b ae : b Æ : b æ : b IgnoreCase : Is AE or ae the same as Æ or æ? AE : f l ae : f l Æ : f l æ : f l No options : Is U" or u" the same as Ü or ü? U" : f l u" : f l Ü : f l ü : f l Ordinal : Is U" or u" the same as Ü or ü? U" : b u" : b Ü : b ü : b IgnoreCase : Is U" or u" the same as Ü or ü? U" : f l u" : f l Ü : f l ü : f l */