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

[This documentation is for preview only, and is subject to change in later releases. Blank topics are included as placeholders.]

Searches a range of elements in a one-dimensional sorted Array for a value, using the specified IComparer interface.

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

Syntax

'Declaration
Public Shared Function BinarySearch ( _
    array As Array, _
    index As Integer, _
    length As Integer, _
    value As Object, _
    comparer As IComparer _
) As Integer

public static int BinarySearch(
    Array array,
    int index,
    int length,
    Object value,
    IComparer comparer
)

public:
static int BinarySearch(
    Array^ array, 
    int index, 
    int length, 
    Object^ value, 
    IComparer^ comparer
)

static member BinarySearch : 
        array:Array * 
        index:int * 
        length:int * 
        value:Object * 
        comparer:IComparer -> int 

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

Parameters

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 null Nothing nullptr unit 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-

comparer is null Nothing nullptr unit 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 null Nothing nullptr unit 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.

Remarks

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 (~) 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 CaseInsensitiveComparer as the comparer to perform case-insensitive string searches.

If comparer is not null Nothing nullptr unit 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 null Nothing nullptr unit 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.

Note

If comparer is null Nothing nullptr unit 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.

null Nothing nullptr unit a null reference (Nothing in Visual Basic) can always be compared with any other reference type; therefore, comparisons with null Nothing nullptr unit a null reference (Nothing in Visual Basic) do not generate an exception when using IComparable. When sorting, null Nothing nullptr unit a 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 implementation, even if value is null Nothing nullptr unit a null reference (Nothing in Visual Basic) . That is, the IComparable implementation determines how a given element compares to null Nothing nullptr unit a null reference (Nothing in Visual Basic) .

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

.NET Framework Security

See Also

Reference

Array Class

BinarySearch Overload

System Namespace