String.IndexOf Method (Char, Int32)
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Reports the zero-based index of the first occurrence of the specified Unicode character in this string. The search starts at a specified character position.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Function IndexOf ( _
value As Char, _
startIndex As Integer _
) As Integer
public int IndexOf(
char value,
int startIndex
)
Parameters
- value
Type: System.Char
A Unicode character to seek.
- startIndex
Type: System.Int32
The search starting position.
Return Value
Type: System.Int32
The zero-based index position of value if that character is found, or -1 if it is not.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentOutOfRangeException | startIndex is less than zero or greater than the length of this string instance. |
Remarks
Index numbering starts from zero. startIndex can range from 0 to one less than the length of the string instance.
The search ranges from startIndex to the end of the string.
The search for value is case-sensitive.
This method performs an ordinal (culture-insensitive) search, where a character is considered equivalent to another character only if their Unicode scalar values are the same. To perform a culture-sensitive search, use the CompareInfo.IndexOf method, where a Unicode scalar value representing a precomposed character, such as the ligature 'Æ' (U+00C6), might be considered equivalent to any occurrence of the character's components in the correct sequence, such as "AE" (U+0041, U+0045), depending on the culture.
Examples
The following code example demonstrates the IndexOf method.
' Sample for String.IndexOf(Char, Int32)
Module Example
Public Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim br1 As String = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-"
Dim br2 As String = "0123456789012345678901234567890123456789012345678901234567890123456"
Dim str As String = "Now is the time for all good men to come to the aid of their party."
Dim start As Integer
Dim at As Integer
outputBlock.Text &= vbCrLf
outputBlock.Text &= String.Format("All occurrences of 't' from position 0 to {0}.", str.Length - 1) & vbCrLf
outputBlock.Text &= String.Format("{1}{0}{2}{0}{3}{0}", vbCrLf, br1, br2, str) & vbCrLf
outputBlock.Text &= "The letter 't' occurs at position(s): "
at = 0
start = 0
While start < str.Length AndAlso at > -1
at = str.IndexOf("t"c, start)
If at = -1 Then
Exit While
End If
outputBlock.Text &= String.Format("{0} ", at)
start = at + 1
End While
outputBlock.Text &= vbCrLf
End Sub
End Module
'
'This example produces the following results:
'
'All occurrences of 't' from position 0 to 66.
'0----+----1----+----2----+----3----+----4----+----5----+----6----+-
'0123456789012345678901234567890123456789012345678901234567890123456
'Now is the time for all good men to come to the aid of their party.
'
'The letter 't' occurs at position(s): 7 11 33 41 44 55 64
'
'
// Sample for String.IndexOf(Char, Int32)
using System;
class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
string br1 = "0----+----1----+----2----+----3----+----4----+----5----+----6----+-";
string br2 = "0123456789012345678901234567890123456789012345678901234567890123456";
string str = "Now is the time for all good men to come to the aid of their party.";
int start;
int at;
outputBlock.Text += "\n";
outputBlock.Text += String.Format("All occurrences of 't' from position 0 to {0}.", str.Length - 1) + "\n";
outputBlock.Text += String.Format("{1}{0}{2}{0}{3}{0}", "\n", br1, br2, str) + "\n";
outputBlock.Text += "The letter 't' occurs at position(s): ";
at = 0;
start = 0;
while ((start < str.Length) && (at > -1))
{
at = str.IndexOf('t', start);
if (at == -1) break;
outputBlock.Text += String.Format("{0} ", at);
start = at + 1;
}
outputBlock.Text += "\n";
}
}
/*
This example produces the following results:
All occurrences of 't' from position 0 to 66.
0----+----1----+----2----+----3----+----4----+----5----+----6----+-
0123456789012345678901234567890123456789012345678901234567890123456
Now is the time for all good men to come to the aid of their party.
The letter 't' occurs at position(s): 7 11 33 41 44 55 64
*/
Version Information
Silverlight
Supported in: 5, 4, 3
Silverlight for Windows Phone
Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0
XNA Framework
Supported in: Xbox 360, Windows Phone OS 7.0
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.
See Also