Array.IndexOf Method (Array, Object, Int32, Int32)
Searches for the specified object in a range of elements of a one-dimensional array, and returns the index of ifs first occurrence. The range extends from a specified index for a specified number of elements.
Assembly: mscorlib (in mscorlib.dll)
Public Shared Function IndexOf ( array As Array, value As Object, startIndex As Integer, count As Integer ) As Integer
Parameters
- array
-
Type:
System.Array
The one-dimensional array to search.
- value
-
Type:
System.Object
The object to locate in array.
- startIndex
-
Type:
System.Int32
The starting index of the search. 0 (zero) is valid in an empty array.
- count
-
Type:
System.Int32
The number of elements to search.
Return Value
Type: System.Int32The index of the first occurrence of value, if it’s found in the array from index startIndex to startIndex + count - 1; otherwise, the lower bound of the array minus 1.
| Exception | Condition |
|---|---|
| ArgumentNullException | array is null. |
| 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. |
| RankException | array is multidimensional. |
This method searches the elements of a one-dimensional arrayfrom startIndexto startIndex plus count minus 1, if count is greater than 0. To determine whether value exists in array, the method performs an equality comparison by calling the Equals method of every element until it finds a match. This means that if the element overrides the Object.Equals method, that override is called.
Becausemost arrays have a lower bound of zero, this method generally returns –1 when value isn’t found. In the rare case that the lower bound of the array is equal to Int32.MinValue (0x80000000) and value isn’t found, this method returns Int32.MaxValue (0x7FFFFFFF).
If startindex equals Array.Length, the method returns -1. If startIndex is greater than Array.Length, the method throws an ArgumentOutOfRangeException.
This method is an O(n) operation, where n is count.
The example calls the following three overloads of the IndexOf method to find the index of a string in a string array:
IndexOf(Array, Object), to determine the first occurrence of the string "the" in a string array.
IndexOf(Array, Object, Int32), to determine the first occurrence of the string "the" in the fourth to the last elements of a string array.
IndexOf(Array, Object, Int32, Int32), to determine the first occurrence of the string "the" in a string array from the element that follows the last successful match to the end of the array. To determine the value of the count argument, it subtracts the upper bound of the array from the starting index and adds one.
Public Module Example Public Sub Main() ' Create a string array with 3 elements having the same value. Dim strings() As String = { "the", "quick", "brown", "fox", "jumps", "over", "the", "lazy", "dog", "in", "the", "barn" } ' Display the values of the array. Console.WriteLine("The array contains the following values:") For i As Integer = strings.GetLowerBound(0) To strings.GetUpperBound(0) Console.WriteLine(" [{0,2}]: {1}", i, strings(i)) Next ' Search for the first occurrence of the duplicated value. Dim searchString As String = "the" Dim index As Integer = Array.IndexOf(strings, searchString) Console.WriteLine("The first occurrence of ""{0}"" is at index {1}.", searchString, index) ' Search for the first occurrence of the duplicated value in the last section of the array. index = Array.IndexOf(strings, searchString, 4) Console.WriteLine("The first occurrence of ""{0}"" between index 4 and the end is at index {1}.", searchString, index) ' Search for the first occurrence of the duplicated value in a section of the array. Dim position As Integer = index + 1 index = Array.IndexOf(strings, searchString, position, strings.GetUpperBound(0) - position + 1) Console.WriteLine("The first occurrence of ""{0}"" between index {1} and index {2} is at index {3}.", searchString, position, strings.GetUpperBound(0), index) End Sub End Module ' The example displays the following output: ' The array contains the following values: ' [ 0]: the ' [ 1]: quick ' [ 2]: brown ' [ 3]: fox ' [ 4]: jumps ' [ 5]: over ' [ 6]: the ' [ 7]: lazy ' [ 8]: dog ' [ 9]: in ' [10]: the ' [11]: barn ' The first occurrence of "the" is at index 0. ' The first occurrence of "the" between index 4 and the end is at index 6. ' The first occurrence of "the" between index 7 and index 11 is at index 10.
Available since 8
.NET Framework
Available since 1.1
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 2.0
Windows Phone Silverlight
Available since 7.0
Windows Phone
Available since 8.1