Array.BinarySearch<(Of <(T>)>) Method (array<T>[]()[], Int32, Int32, T, IComparer<(Of <(T>)>))

[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]

Searches a range of elements in a one-dimensional sorted Array for a value, using the specified IComparer<(Of <(T>)>) generic interface.

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

Syntax

Public Shared Function BinarySearch(Of T) ( _
    array As T(), _
    index As Integer, _
    length As Integer, _
    value As T, _
    comparer As IComparer(Of T) _
) As Integer
public static int BinarySearch<T>(
    T[] array,
    int index,
    int length,
    T value,
    IComparer<T> comparer
)

Type Parameters

  • T
    The type of the elements of the array.

Parameters

  • array
    Type: array<T>[]()[]
    The sorted one-dimensional, zero-based Array to search.
  • value
    Type: T
    The object to search for.

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).

Exceptions

Exception Condition
ArgumentNullException

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

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-

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

InvalidOperationException

comparer is nullNothingnullptra null reference (Nothing in Visual Basic), value does not implement the IComparable<(Of <(T>)>) generic interface, and the search encounters an element that does not implement the IComparable<(Of <(T>)>) generic interface.

Remarks

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.

If comparer is not nullNothingnullptra null reference (Nothing in Visual Basic), the elements of array are compared to the specified value using the specified IComparer<(Of <(T>)>) generic interface 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 nullNothingnullptra null reference (Nothing in Visual Basic), the comparison is done using the IComparable<(Of <(T>)>) generic interface 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<(Of <(T>)>) implementation; otherwise, the result might be incorrect.

Note

If comparer is nullNothingnullptra null reference (Nothing in Visual Basic) and value does not implement the IComparable<(Of <(T>)>) generic interface, the elements of array are not tested for IComparable<(Of <(T>)>) before the search begins. An exception is thrown if the search encounters an element that does not implement IComparable<(Of <(T>)>).

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.

nullNothingnullptra null reference (Nothing in Visual Basic) can always be compared with any other reference type; therefore, comparisons with nullNothingnullptra null reference (Nothing in Visual Basic) do not generate an exception when using IComparable<(Of <(T>)>). When sorting, nullNothingnullptra null reference (Nothing in Visual Basic) is considered to be less than any other object.

Note

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

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

Version Information

Windows Phone OS

Supported in: 8.1, 8.0, 7.1, 7.0

Platforms

Windows Phone

See Also

Reference

Array Class

BinarySearch Overload

System Namespace

IComparer<(Of <(T>)>)

IComparable<(Of <(T>)>)

Sort