String.LastIndexOf Method (String)

July 28, 2014

Reports the zero-based index position of the last occurrence of a specified string within this instance.

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

public int LastIndexOf(
	string value
)

Parameters

value
Type: System.String
The string to seek.

Return Value

Type: System.Int32
The zero-based index position of value 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 null.

Index numbering starts from zero. That is, the first character in the string is at index zero, and the last is at Length - 1.

This method performs a word (case-sensitive and culture-sensitive) search using the current culture. The search begins at the last character position of this instance and proceeds backward, until either value is found or the first character position has been examined.

The following example removes opening and closing HTML tags from a string if the tags begin and end the string. If a string ends with a closing bracket character (">"), the example uses the LastIndexOf method to locate the start of the end tag.


using System;

public class Example
{
   public static void Demo(System.Windows.Controls.TextBlock outputBlock)
   {
      string[] strSource = { "<b>This is bold text</b>", "<H1>This is large Text</H1>",
               "<b><i><font color=green>This has multiple tags</font></i></b>",
               "<b>This has <i>embedded</i> tags.</b>",
               "This line ends with a greater than symbol and should not be modified>" };

      // Strip HTML start and end tags from each string if they are present.
      foreach (string s in strSource)
      {
         outputBlock.Text += "Before: " + s + "\n";
         string item = s;
         // Use EndsWith to find a tag at the end of the line.
         if (item.Trim().EndsWith(">"))
         {
            // Locate the opening tag.
            int endTagStartPosition = item.LastIndexOf("</");
            // Remove the identified section, if it is valid.
            if (endTagStartPosition >= 0)
               item = item.Substring(0, endTagStartPosition);

            // Use StartsWith to find the opening tag.
            if (item.Trim().StartsWith("<"))
            {
               // Locate the end of opening tab.
               int openTagEndPosition = item.IndexOf(">");
               // Remove the identified section, if it is valid.
               if (openTagEndPosition >= 0)
                  item = item.Substring(openTagEndPosition + 1);
            }
         }
         // Display the trimmed string.
         outputBlock.Text += "After: " + item + "\n";
         outputBlock.Text += "\n";
      }
   }
}
// The example displays the following output:
//    Before: <b>This is bold text</b>
//    After: This is bold text
//    
//    Before: <H1>This is large Text</H1>
//    After: This is large Text
//    
//    Before: <b><i><font color=green>This has multiple tags</font></i></b>
//    After: <i><font color=green>This has multiple tags</font></i>
//    
//    Before: <b>This has <i>embedded</i> tags.</b>
//    After: This has <i>embedded</i> tags.
//    
//    Before: This line ends with a greater than symbol and should not be modified>
//    After: This line ends with a greater than symbol and should not be modified>


Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Windows Phone

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