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
)

Parameters

array
Type: System::Array

The sorted one-dimensional Array to search.

value
Type: System::Object

The object to search for.

comparer
Type: System.Collections::IComparer

The IComparer implementation to use when comparing elements.

-or-

nullptr to use the IComparable implementation of each element.

Return Value

Type: System::Int32
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).

ExceptionCondition
ArgumentNullException

array is nullptr.

RankException

array is multidimensional.

ArgumentException

comparer is nullptr, and value is of a type that is not compatible with the elements of array.

InvalidOperationException

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

This method does not support searching arrays that contain negative indexes. array must be sorted before calling this method.

If the Array does not contain the specified value, the method returns a negative integer. You can apply the bitwise complement operator (~ in C#, Not in Visual Basic) to the negative result to produce an index. If this index is one greater than the upper bound 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 nullptr, 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 nullptr, 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 nullptr 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.

nullptr can always be compared with any other reference type; therefore, comparisons with nullptr do not generate an exception.

NoteNote

For every element tested, value is passed to the appropriate IComparable implementation, even if value is nullptr. That is, the IComparable implementation determines how a given element compares to nullptr.

This method is an O(log n) operation, where n is the Length of array.

.NET Framework

Supported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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