Export (0) Print
Expand All
Information
The topic you requested is included in another documentation set. For convenience, it's displayed below. Choose Switch to see the topic in its original location.

String.IndexOf Method (String, StringComparison)

July 28, 2014

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

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

public int IndexOf(
	string value,
	StringComparison comparisonType
)

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 index position of the value parameter if that string is found, or -1 if it is not. If value is Empty, the return value is 0.

ExceptionCondition
ArgumentNullException

value is null.

ArgumentException

comparisonType is not a valid System.StringComparison value.

Index numbering starts from zero.

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 following code example demonstrates three overloads of the IndexOf method that find the first occurrence of a string within another string using different values of the StringComparison enumeration.


// This code example demonstrates the 
// System.String.IndexOf(String, ..., StringComparison) methods.

using System;
using System.Threading;
using System.Globalization;

class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      string intro = "Find the first occurrence of a character using different " +
                     "values of StringComparison.";
      string resultFmt = "Comparison: {0,-28} Location: {1,3}";

      // Define a string to search for.
      // U+00c5 = LATIN CAPITAL LETTER A WITH RING ABOVE
      string CapitalAWithRing = "\u00c5";

      // Define a string to search. 
      // The result of combining the characters LATIN SMALL LETTER A and COMBINING 
      // RING ABOVE (U+0061, U+030a) is linguistically equivalent to the character 
      // LATIN SMALL LETTER A WITH RING ABOVE (U+00e5).
      string cat = "A Cheshire c" + "\u0061\u030a" + "t";

      int loc = 0;
      StringComparison[] scValues = {
        StringComparison.CurrentCulture,
        StringComparison.CurrentCultureIgnoreCase,
        StringComparison.InvariantCulture,
        StringComparison.InvariantCultureIgnoreCase,
        StringComparison.Ordinal,
        StringComparison.OrdinalIgnoreCase };

      // Display an introduction.
      outputBlock.Text += intro + "\n";

      // Display the current culture because culture affects the result. For example, 
      // try this code example with the "sv-SE" (Swedish-Sweden) culture.

      Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
      outputBlock.Text += String.Format("The current culture is \"{0}\" - {1}.",
                         Thread.CurrentThread.CurrentCulture.Name,
                         Thread.CurrentThread.CurrentCulture.DisplayName) + "\n";

      // Display the string to search for and the string to search.
      outputBlock.Text += String.Format("Search for the string \"{0}\" in the string \"{1}\"",
                         CapitalAWithRing, cat) + "\n";
      outputBlock.Text += "\n";

      // Note that in each of the following searches, we look for 
      // LATIN CAPITAL LETTER A WITH RING ABOVE in a string that contains 
      // LATIN SMALL LETTER A WITH RING ABOVE. A result value of -1 indicates 
      // the string was not found.
      // Search using different values of StringComparison. Specify the start 
      // index and count. 

      outputBlock.Text += "Part 1: Start index and count are specified." + "\n";
      foreach (StringComparison sc in scValues)
      {
         loc = cat.IndexOf(CapitalAWithRing, 0, cat.Length, sc);
         outputBlock.Text += String.Format(resultFmt, sc, loc) + "\n";
      }

      // Search using different values of StringComparison. Specify the 
      // start index. 
      outputBlock.Text += "\nPart 2: Start index is specified." + "\n";
      foreach (StringComparison sc in scValues)
      {
         loc = cat.IndexOf(CapitalAWithRing, 0, sc);
         outputBlock.Text += String.Format(resultFmt, sc, loc) + "\n";
      }

      // Search using different values of StringComparison. 
      outputBlock.Text += "\nPart 3: Neither start index nor count is specified." + "\n";
      foreach (StringComparison sc in scValues)
      {
         loc = cat.IndexOf(CapitalAWithRing, sc);
         outputBlock.Text += String.Format(resultFmt, sc, loc) + "\n";
      }
   }
}

/*
Note: This code example was executed on a console whose user interface 
culture is "en-US" (English-United States).

This code example produces the following results:

Find the first occurrence of a character using different values of StringComparison.
The current culture is "en-US" - English (United States).
Search for the string "Å" in the string "A Cheshire ca°t"

Part 1: Start index and count are specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 2: Start index is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

Part 3: Neither start index nor count is specified.
Comparison: CurrentCulture               Location:  -1
Comparison: CurrentCultureIgnoreCase     Location:  12
Comparison: InvariantCulture             Location:  -1
Comparison: InvariantCultureIgnoreCase   Location:  12
Comparison: Ordinal                      Location:  -1
Comparison: OrdinalIgnoreCase            Location:  -1

*/


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

Show:
© 2014 Microsoft