Array.LastIndexOf(T) Method (T, T)
Searches for the specified object and returns the index of the last occurrence within the entire Array.
Assembly: mscorlib (in mscorlib.dll)
The type of the elements of the array.
- Type: 
The one-dimensional, zero-based Array to search.
The object to locate in array.
Return ValueType: System.Int32
The zero-based index of the last occurrence of value within the entire array, if found; otherwise, –1.
array is a null reference (Nothing in Visual Basic).
The Array is searched backward starting at the last element and ending at the first element.
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.
This method is an O(n) operation, where n is the Length of array.
The following code example demonstrates all three generic overloads of the LastIndexOf method. An array of strings is created, with one entry that appears twice, at index location 0 and index location 5. The method overload searches the entire array from the end, and finds the second occurrence of the string. The LastIndexOf(T)(T, T, Int32) method overload is used to search the array backward beginning with index location 3 and continuing to the beginning of the array, and finds the first occurrence of the string. Finally, the LastIndexOf(T)(T, T, Int32, Int32) method overload is used to search a range of four entries, beginning at index location 4 and extending backward (that is, it searches the items at locations 4, 3, 2, and 1); this search returns –1 because there are no instances of the search string in that range.
.NET FrameworkSupported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0
.NET Framework Client ProfileSupported in: 4, 3.5 SP1
XNA FrameworkSupported in: 3.0, 2.0, 1.0
Portable Class LibrarySupported in: Portable Class Library
Supported in: Windows Phone 8.1
Supported in: Windows Phone Silverlight 8.1
Supported in: Windows Phone Silverlight 8