Element Operators : Last & LastOrDefault
The Last() and LastOrDefault() extension methods returns the last element from the collection.
| Element Operators | Description |
|---|---|
| Last() | Returns the last element from a collection, or the last element that satisfies a condition. Throws exception if no element found. |
| LastOrDefault() | Returns the last element from a collection, or the last element that satisfies a condition. Returns a default value if no element found. |
public static TSource Last<TSource>(this IEnumerable<TSource> source); public static TSource Last<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate); public static TSource LastOrDefault<TSource>(this IEnumerable<TSource> source); public static TSource LastOrDefault<TSource>(this IEnumerable<TSource> source, Func<TSource, bool> predicate);
The Last() method returns the last element from a collection, or the last element that satisfies the specified condition using lambda expression or Func delegate. If a given collection is empty or does not include any element that satisfied the condition then it will throw InvalidOperation exception.
The LastOrDefault() method does the same thing as the Last() method. The only difference is that it returns default value of the data type of a collection if a collection is empty or doesn't find any element that satisfies the condition.
IList<int> intList = new List<int>() { 7, 10, 21, 30, 45, 50, 87 };
IList<string> strList = new List<string>() { null, "Two", "Three", "Four", "Five" };
IList<string> emptyList = new List<string>();
Console.WriteLine("Last Element in intList: {0}", intList.Last());
Console.WriteLine("Last Even Element in intList: {0}", intList.Last(i => i % 2 == 0));
Console.WriteLine("Last Element in strList: {0}", strList.Last());
Console.WriteLine("emptyList.Last() throws an InvalidOperationException");
Console.WriteLine("-------------------------------------------------------------");
Console.WriteLine(emptyList.Last());Last Even Element in intList: 50
Last Element in strList: Five
emptyList.Last() throws an InvalidOperationException
-------------------------------------------------------------
Run-time exception: Sequence contains no elements...
The following example demonstrates the LastOrDefault() method.
IList<int> intList = new List<int>() { 7, 10, 21, 30, 45, 50, 87 };
IList<string> strList = new List<string>() { null, "Two", "Three", "Four", "Five" };
IList<string> emptyList = new List<string>();
Console.WriteLine("Last Element in intList: {0}", intList.LastOrDefault());
Console.WriteLine("Last Even Element in intList: {0}",
intList.LastOrDefault(i => i % 2 == 0));
Console.WriteLine("Last Element in strList: {0}", strList.LastOrDefault());
Console.WriteLine("Last Element in emptyList: {0}", emptyList.LastOrDefault());Last Even Element in intList: 50
Last Element in strList: Five
Last Element in emptyList:
Be careful while specifying condition in the Last() or LastOrDefault() methods. The Last() method will throw an exception if a collection does not include any element that satisfies the specified condition or includes null element.
If a collection includes null element then the LastOrDefault() throws an exception while evaluting the specified condition.
IList<string> strList1 = new List<string>() { "Two", "Three", "Four", "Five" };
IList<string> strList2 = new List<string>() { null, "Two", "Three", "Four", "Five" };
Console.WriteLine(strList1.LastOrDefault(s => s.Contains("T")));
Console.WriteLine(strList2.LastOrDefault(s => s.Contains("T")));// throws an exception