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ArrayList.BinarySearch Method (Object, IComparer)

Searches the entire sorted ArrayList for an element using the specified comparer and returns the zero-based index of the element.

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

public virtual int BinarySearch (
	Object value,
	IComparer comparer
)
public int BinarySearch (
	Object value, 
	IComparer comparer
)
public function BinarySearch (
	value : Object, 
	comparer : IComparer
) : int
Not applicable.

Parameters

value

The Object to locate. The value can be a null reference (Nothing in Visual Basic).

comparer

The IComparer implementation to use when comparing elements.

-or-

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

Return Value

The zero-based index of value in the sorted ArrayList, if value is found; otherwise, a negative number, which is the bitwise complement of the index of the next element that is larger than value or, if there is no larger element, the bitwise complement of Count.

Exception typeCondition

ArgumentException

comparer is a null reference (Nothing in Visual Basic) and neither value nor the elements of ArrayList implement the IComparable interface.

InvalidOperationException

comparer is a null reference (Nothing in Visual Basic) and value is not of the same type as the elements of the ArrayList.

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

If comparer is provided, the elements of the ArrayList are compared to the specified value using the specified IComparer implementation. The elements of the ArrayList 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 the ArrayList must already be sorted in increasing value according to the sort order defined by the IComparable implementation; otherwise, the result might be incorrect.

Comparing a null reference (Nothing in Visual Basic) with any type is allowed and does not generate an exception when using IComparable. When sorting, a null reference (Nothing in Visual Basic) is considered to be less than any other object.

If the ArrayList contains more than one element with the same value, the method returns only one of the occurrences, and it might return any one of the occurrences, not necessarily the first one.

If the ArrayList does not contain the specified value, the method returns a negative integer. You can apply the bitwise complement operation (~) to this negative integer to get the index of the first element that is larger than the search value. When inserting the value into the ArrayList, this index should be used as the insertion point to maintain the sort order.

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

Windows 98, Windows Server 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 Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

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