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Array.BinarySearch Method (Array, Int32, Int32, Object)

Searches a range of elements in a one-dimensional sorted Array for a value, using the IComparable interface implemented by each element of the Array and by the specified value.

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

public static int BinarySearch (
	Array array,
	int index,
	int length,
	Object value
)
public static int BinarySearch (
	Array array, 
	int index, 
	int length, 
	Object value
)
public static function BinarySearch (
	array : Array, 
	index : int, 
	length : int, 
	value : Object
) : int

Parameters

array

The sorted one-dimensional Array to search.

index

The starting index of the range to search.

length

The length of the range to search.

value

The object to search for.

Return Value

The index of the specified value in the specified array, if value is found. If value is not found and value is less than one or more elements in array, a negative number which is the bitwise complement of the index of the first element that is larger than value. If value is not found and value is greater than any of the elements in array, a negative number which is the bitwise complement of (the index of the last element plus 1).

Exception typeCondition

ArgumentNullException

array is a null reference (Nothing in Visual Basic).

RankException

array is multidimensional.

ArgumentOutOfRangeException

index is less than the lower bound of array.

-or-

length is less than zero.

ArgumentException

index and length do not specify a valid range in array.

-or-

value is of a type that is not compatible with the elements of array.

InvalidOperationException

value does not implement the IComparable interface, and the search encounters an element that does not implement the IComparable interface.

If the Array does not contain the specified value, the method returns a negative integer. You can apply the bitwise complement operator (~) to the negative result (in Visual Basic, Xor the negative result with -1) to produce an index. If this index is greater than or equal to the size of the array, there are no elements larger than value in the array. Otherwise, it is the index of the first element that is larger than value.

Either value or every element of array must implement the IComparable interface, which is used for comparisons. The elements of array must already be sorted in increasing value according to the sort order defined by the IComparable implementation; otherwise, the result might be incorrect.

NoteNote

If value does not implement the IComparable interface, the elements of array are not tested for IComparable before the search begins. An exception is thrown if the search encounters an element that does not implement IComparable.

Duplicate elements are allowed. If the Array contains more than one element equal to value, the method returns the index of only one of the occurrences, and not necessarily the first one.

a null reference (Nothing in Visual Basic) can always be compared with any other reference type; therefore, comparisons with a null reference (Nothing in Visual Basic) do not generate an exception. When sorting, a null reference (Nothing in Visual Basic) is considered to be less than any other object.

NoteNote

   For every element tested, value is passed to the appropriate IComparable implementation, even if value is a null reference (Nothing in Visual Basic). That is, the IComparable implementation determines how a given element compares to a null reference (Nothing in Visual Basic).

This method is an O(log n) operation, where n is length.

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0

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