Array.IndexOf<T> Method (array<T[], T, Int32, Int32)
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Searches for the specified object and returns the index of the first occurrence within the range of elements in the Array that starts at the specified index and contains the specified number of elements.
Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Syntax
'Declaration
Public Shared Function IndexOf(Of T) ( _
array As T(), _
value As T, _
startIndex As Integer, _
count As Integer _
) As Integer
public static int IndexOf<T>(
T[] array,
T value,
int startIndex,
int count
)
Type Parameters
- T
The type of the elements of the array.
Parameters
- array
Type: array<T[]
The one-dimensional, zero-based Array to search.
- value
Type: T
The object to locate in array.
- startIndex
Type: System.Int32
The zero-based starting index of the search.
- count
Type: System.Int32
The number of elements in the section to search.
Return Value
Type: System.Int32
The zero-based index of the first occurrence of value within the range of elements in array that starts at startIndex and contains the number of elements specified in count, if found; otherwise, –1.
Exceptions
| Exception | Condition |
|---|---|
| ArgumentNullException | array is nulla null reference (Nothing in Visual Basic). |
| ArgumentOutOfRangeException | startIndex is outside the range of valid indexes for array. -or- count is less than zero. -or- startIndex and count do not specify a valid section in array. |
Remarks
The Array is searched forward starting at startIndex and ending at startIndex plus count minus 1, if count is greater than 0.
The elements are compared to the specified value using the Object.Equals method. If the element type is a nonintrinsic (user-defined) type, the Equals implementation of that type is used.
Passing the Length property of the array as the startindex parameter results in a return value of -1; passing values greater than Length raises an ArgumentOutOfRangeException.
This method is an O(n) operation, where n is count.
Examples
The following code example demonstrates all three generic overloads of the IndexOf method. An array of strings is created, with one entry that appears twice, at index location 0 and index location 5. The IndexOf<T>(array<T[], T) method overload searches the array from the beginning, and finds the first occurrence of the string. The IndexOf<T>(array<T[], T, Int32) method overload is used to search the array beginning with index location 3 and continuing to the end of the array, and finds the second occurrence of the string. Finally, the IndexOf<T>(array<T[], T, Int32, Int32) method overload is used to search a range of two entries, beginning at index location two; it returns –1 because there are no instances of the search string in that range.
Public Class Example
Public Shared Sub Demo(ByVal outputBlock As System.Windows.Controls.TextBlock)
Dim dinosaurs() As String = {"Tyrannosaurus", _
"Amargasaurus", _
"Mamenchisaurus", _
"Brachiosaurus", _
"Deinonychus", _
"Tyrannosaurus", _
"Compsognathus"}
outputBlock.Text &= vbCrLf
For Each dinosaur As String In dinosaurs
outputBlock.Text &= dinosaur & vbCrLf
Next
outputBlock.Text &= String.Format(vbLf & _
"Array.IndexOf(dinosaurs, ""Tyrannosaurus""): {0}", _
Array.IndexOf(dinosaurs, "Tyrannosaurus")) & vbCrLf
outputBlock.Text &= String.Format(vbLf & _
"Array.IndexOf(dinosaurs, ""Tyrannosaurus"", 3): {0}", _
Array.IndexOf(dinosaurs, "Tyrannosaurus", 3)) & vbCrLf
outputBlock.Text &= String.Format(vbLf & _
"Array.IndexOf(dinosaurs, ""Tyrannosaurus"", 2, 2): {0}", _
Array.IndexOf(dinosaurs, "Tyrannosaurus", 2, 2)) & vbCrLf
End Sub
End Class
' This code example produces the following output:
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Brachiosaurus
'Deinonychus
'Tyrannosaurus
'Compsognathus
'
'Array.IndexOf(dinosaurs, "Tyrannosaurus"): 0
'
'Array.IndexOf(dinosaurs, "Tyrannosaurus", 3): 5
'
'Array.IndexOf(dinosaurs, "Tyrannosaurus", 2, 2): -1
using System;
public class Example
{
public static void Demo(System.Windows.Controls.TextBlock outputBlock)
{
string[] dinosaurs = { "Tyrannosaurus",
"Amargasaurus",
"Mamenchisaurus",
"Brachiosaurus",
"Deinonychus",
"Tyrannosaurus",
"Compsognathus" };
outputBlock.Text += "\n";
foreach (string dinosaur in dinosaurs)
{
outputBlock.Text += dinosaur + "\n";
}
outputBlock.Text += String.Format(
"\nArray.IndexOf(dinosaurs, \"Tyrannosaurus\"): {0}",
Array.IndexOf(dinosaurs, "Tyrannosaurus")) + "\n";
outputBlock.Text += String.Format(
"\nArray.IndexOf(dinosaurs, \"Tyrannosaurus\", 3): {0}",
Array.IndexOf(dinosaurs, "Tyrannosaurus", 3)) + "\n";
outputBlock.Text += String.Format(
"\nArray.IndexOf(dinosaurs, \"Tyrannosaurus\", 2, 2): {0}",
Array.IndexOf(dinosaurs, "Tyrannosaurus", 2, 2)) + "\n";
}
}
/* This code example produces the following output:
Tyrannosaurus
Amargasaurus
Mamenchisaurus
Brachiosaurus
Deinonychus
Tyrannosaurus
Compsognathus
Array.IndexOf(dinosaurs, "Tyrannosaurus"): 0
Array.IndexOf(dinosaurs, "Tyrannosaurus", 3): 5
Array.IndexOf(dinosaurs, "Tyrannosaurus", 2, 2): -1
*/
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.