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Array.BinarySearch Method (Array, Object, IComparer)

Searches an entire one-dimensional sorted Array for a value using the specified IComparer interface.

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

public static int BinarySearch (
	Array array,
	Object value,
	IComparer comparer
)
public static int BinarySearch (
	Array array, 
	Object value, 
	IComparer comparer
)
public static function BinarySearch (
	array : Array, 
	value : Object, 
	comparer : IComparer
) : int

Parameters

array

The sorted one-dimensional Array to search.

value

The object to search for.

comparer

The IComparer implementation to use when comparing elements.

-or-

a null reference (Nothing in Visual Basic) to use the IComparable implementation of each element.

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.

ArgumentException

comparer is a null reference (Nothing in Visual Basic), and value is of a type that is not compatible with the elements of array.

InvalidOperationException

comparer is a null reference (Nothing in Visual Basic), 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.

The comparer customizes how the elements are compared. For example, you can use a System.Collections.CaseInsensitiveComparer as the comparer to perform case-insensitive string searches.

If comparer is not a null reference (Nothing in Visual Basic), the elements of array are compared to the specified value using the specified IComparer implementation. The elements of array must already be sorted in increasing value according to the sort order defined by comparer; otherwise, the result might be incorrect.

If comparer is a null reference (Nothing in Visual Basic), the comparison is done using the IComparable implementation provided by the element itself or by the specified value. 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 comparer is a null reference (Nothing in Visual Basic) and 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 the Length of array.

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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