ElementAtOrDefault Use
This page was last reviewed on Dec 7, 2023.
Dot Net Perls
ElementAtOrDefault. The C# ElementAtOrDefault method accesses an element. It handles an out-of-range access without throwing an exception.
ElementAtOrDefault returns a default value if the index is not present. ElementAt meanwhile will throw an error on nonexistent indexes.
Example. In this program we create a 3-element array. The only valid indexes to access are 0, 1 and 2. We show how ElementAtOrDefault works on valid indexes, and also out-of-range indexes.
int Array
Tip On out-of-range accesses, ElementAtOrDefault returns the default value for the type, which for int is 0.
int, uint
using System; using System.Linq; int[] array = { 4, 5, 6 }; // Call ElementAtOrDefault with various indexes. int a = array.ElementAtOrDefault(0); int b = array.ElementAtOrDefault(1); int c = array.ElementAtOrDefault(-1); int d = array.ElementAtOrDefault(1000); Console.WriteLine(a); Console.WriteLine(b); Console.WriteLine(c); Console.WriteLine(d);
4 5 0 0
ElementAt. This method gets an element at an index. In many IEnumerable types, you cannot directly index a certain element. ElementAt can help with these types.
Here This program uses an array of 3 string literal elements. Arrays are IEnumerable collections.
And We can index this array through the ElementAt method in the System.Linq namespace.
Warning The method call with argument 3 throws a System.ArgumentOutOfRangeException.
using System; using System.Linq; // Input array. string[] array = { "Dot", "Net", "Perls" }; // Test ElementAt for 0, 1, 2. string a = array.ElementAt(0); Console.WriteLine(a); string b = array.ElementAt(1); Console.WriteLine(b); string c = array.ElementAt(2); Console.WriteLine(c); // This is out of range. string d = array.ElementAt(3);
Dot Net Perls Unhandled Exception: System.ArgumentOutOfRangeException: Index was out of range.
Index from end. With the "^" syntax, we can access an index from the end of a collection. So "^2" will get the second-to-last element.
Note This syntax is the same as the end-indexing syntax available for lists and arrays in C#.
using System; using System.Linq; var values = new char[] {'a', 'b', 'c', 'd'}; // Use "^" to index from the end. var secondToLast = values.ElementAtOrDefault(^2); Console.WriteLine(secondToLast);
An important note. Conceptually, ElementAtOrDefault can make a collection be infinite. It can make every possible index returning a valid value—the default value.
And This could be useful if a collection is queried for invalid indexes, and actual stored values are not necessary for the algorithm.
These methods can transform how we access collections. ElementAtOrDefault eliminates the need for bounds-checking, but it can create extra complexity when handling the default value.
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
This page was last updated on Dec 7, 2023 (edit).
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