Array.LastIndexOf Method (Array, Object, Int32, Int32)
Searches for the specified object and returns the index of the last occurrence within the range of elements in the one-dimensional Array that contains the specified number of elements and ends at the specified index.
Assembly: mscorlib (in mscorlib.dll)
static member LastIndexOf : array:Array * value:Object * startIndex:int * count:int -> int
- Type: System.Object
The object to locate in array.
- Type: System.Int32
The starting index of the backward search.
- Type: System.Int32
The number of elements in the section to search.
Return ValueType: System.Int32
The index of the last occurrence of value within the range of elements in array that contains the number of elements specified in count and ends at startIndex, if found; otherwise, the lower bound of the array minus 1.
array is a null reference (Nothing in Visual Basic).
startIndex is outside the range of valid indexes for array.
count is less than zero.
startIndex and count do not specify a valid section in array.
array is multidimensional.
The one-dimensional Array is searched backward starting at startIndex and ending at startIndex minus count plus 1, if count is greater than 0.
The elements are compared to the specified value using the Object.Equals 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 Int32.MinValue and value is not found, this method returns Int32.MaxValue, which is System.Int32.MinValue - 1.
This method is an O(n) operation, where n is count.
In the .NET Framework version 2.0, this method uses the Equals and CompareTo 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 Equals and CompareTo methods of the value Object itself.
The following code example shows how to determine the index of the last occurrence of a specified element in an array. Note that the LastIndexOf method is a backward search; therefore, count must be less than or equal to (startIndex minus the lower bound of the array plus 1).