Array.BinarySearch Method (Array, Int32, Int32, Object, IComparer)
Searches a range of elements in a one-dimensional sorted array for a value, using the specified IComparer interface.
Assembly: mscorlib (in mscorlib.dll)
public static int BinarySearch( Array array, int index, int length, Object value, IComparer comparer )
- Type: System.Int32
The starting index of the range to search.
- Type: System.Int32
The length of the range to search.
- Type: System.Object
The object to search for.
Return ValueType: 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).
array is null.
array is multidimensional.
index is less than the lower bound of array.
length is less than zero.
index and length do not specify a valid range in array.
comparer is null, and value is of a type that is not compatible with the elements of array.
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 null, 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, 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.
If comparer is null 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 can always be compared with any other reference type; therefore, comparisons with null do not generate an exception when using IComparable.
For every element tested, value is passed to the appropriate IComparable implementation, even if value is null. That is, the IComparable implementation determines how a given element compares to null.
This method is an O(log n) operation, where n is length.
.NET FrameworkSupported in: 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0
.NET Framework Client ProfileSupported in: 4, 3.5 SP1
Portable Class LibrarySupported in: Portable Class Library
.NET for Windows Store appsSupported in: Windows 8
.NET for Windows Phone appsSupported 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.