System.Array.LastIndexOf Method

Searches for the specified object and returns the index of the last occurrence within the range of elements in the one-dimensional Array that extends from the first element to the specified index.

Syntax

[System.Runtime.ConstrainedExecution.ReliabilityContract(System.Runtime.ConstrainedExecution.Consistency.WillNotCorruptState, System.Runtime.ConstrainedExecution.Cer.MayFail)]
public static int LastIndexOf (Array array, object value, int startIndex)

Parameters

array
The one-dimensional Array to search.
value
The object to locate in array.
startIndex
The starting index of the backward search.

Returns

The index of the last occurrence of value within the range of elements in array that extends from the first element to startIndex, if found; otherwise, the lower bound of the array minus 1.

Exceptions

TypeReason
ArgumentNullException array is null.
ArgumentOutOfRangeException startIndex is outside the range of valid indices for array.
RankException array has more than one dimension.

Remarks

The one-dimensional Array is searched backward starting at startIndex and ending at the first element.

The elements are compared to the specified value using the object.Equals(object) method. If the element type is a nonintrinsic (user-defined) type, the Equals implementation of that type is used.

Since most arrays will have a lower bound of zero, this method would generally return –1 when value is not found. In the rare case that the lower bound of the array is equal to int.MinValue and value is not found, this method returns int.MaxValue, which is System.Int32.MinValue - 1.

This method is an O(n) operation, where n is the number of elements from the beginning of array to startIndex.

In the .NET Framework version 2.0, this method uses the object.Equals(object) and IComparable.CompareTo(object) methods of the Array to determine whether the object specified by the value parameter exists. In the earlier versions of the .NET Framework, this determination was made by using the object.Equals(object) and IComparable.CompareTo(object) methods of the value object itself.

Requirements

Namespace: System
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0