This method is used to search for an element which matches the conditions defined by a specified predicate and returns the zero-based index of the last occurrence within the List<T> or a portion of it. There are 3 methods in the overload list of this method:
Here, we will discuss only the last two methods.
FindLastIndex(Int32, Predicate<T>) Method
This method searches for an element that matches the conditions defined by the specified predicate and returns the zero-based index of the last occurrence within the range of elements in the
List<T> that extends from the first element to the specified index.
Syntax: public int FindLastIndex (int start, Predicate<T> match);
Parameters:
start: It is the starting index from the searching will starts.
match: It is the Predicate delegate that defines the conditions of the searched element.
Return Value: If the element is found then it returns the zero-based index of type
Int32 of the last occurrence of an element that matches a specified condition by the parameter “
match”. And if not found then it returns “
-1”.
Exceptions:
- ArgumentNullException: If the match is null.
- ArgumentOutOfRangeException: If the startis outside the range of valid indexes for the List<T>.
Below programs illustrate the use of above-discussed method:
Example 1:
Output:
0
Example 2:
Output:
2
Example 3: In this example we use an XML file and search an item from a starting index and prints the index of that item, if the item is not found then prints “-1” and if found then prints the index. The item is “
GeeksForGeeks”. But here we don’t have the XML file, and here the compiler gives an exception.
Runtime Error:
Unhandled Exception:
System.ArgumentOutOfRangeException: ArgumentOutOfRange_Index
Parameter name: startIndex
FindLastIndex(Int32, Int32, Predicate<T>) Method
This method searches for an element that matches the conditions defined by the specified predicate and returns the zero-based index of the last occurrence within the entire List and the list contains the specified number of elements and ends at the specified index.
Syntax: public int FindLastIndex (int startIndex, int count, Predicate<T> match);
Parameters:
startIndex: It is the zero-based starting index of the backward search.
count: It is the number of elements in the section to search.
match: It is the Predicate<T> delegate that defines the conditions of the element to search for.
Return Value: If the element is found then it returns the zero-based index of type Int32 of the last element that matches a specified condition by the parameter “match”. And if not found then it returns “-1”.
Exceptions:
- ArgumentNullException: if the “match” is null.
- ArgumentOutOfRangeException: if “startIndex” is outside the range or “count” is less than 0(Zero) or “startIndex” and “count” do not specify a valid section in the List
Example:
