GenericExtensionsBinarySearchT(IListT, FuncT, Int32) Method

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

This differs from the "ordinary" binary search in allowing a comparer delegate that defines whether an item is found (returning 0), whether the item in the list is before (<0) or after (>0) that knows how to compare a class with its key. Example, if the list contains classes of type T having an id number and the class is sorted on that id, then the keySelector returns the id number for that class.

Example

If having a list of doubles, to find 4.5 in the list, use:


            int index = list.BinarySearch(d => d.CompareTo(4.5))

Definition

Namespace: DHI.Mike1D.Generic
Assembly: DHI.Mike1D.Generic (in DHI.Mike1D.Generic.dll) Version: 24.0.0.0 (11.1.1.1111)

C#

public static int BinarySearch<T>(
	this IList<T> list,
	Func<T, int> comparer
)

Parameters

list IListT: List to search in
comparer FuncT, Int32: A delegate/lambda expression specifying if a given item in the list is before (<0), matches (0) or is after (>0) the item to search for.

Type Parameters

T: The type of the objects in the list

Return Value

Int32
The zero-based index of item in the sorted IListT, if item is found; otherwise, a negative number that is the bitwise complement of the index of the next element that is larger than item or, if there is no larger element, the bitwise complement of Count.

Usage Note

In Visual Basic and C#, you can call this method as an instance method on any object of type IListT. When you use instance method syntax to call this method, omit the first parameter. For more information, see Extension Methods (Visual Basic) or Extension Methods (C# Programming Guide).