Defaults & generators in C#

Empty sequences without the exceptions.

var empty = Array.Empty<int>();

// FirstOrDefault hands back a default instead of throwing
Console.WriteLine(empty.FirstOrDefault());
Console.WriteLine(empty.FirstOrDefault(-1));

// DefaultIfEmpty keeps aggregate math safe on empty input
Console.WriteLine(empty.DefaultIfEmpty(0).Average());

// Range and Repeat conjure sequences from nothing
Console.WriteLine(string.Join(",", Enumerable.Range(5, 4)));
Console.WriteLine(string.Join(",", Enumerable.Repeat("ok", 3)));

How it works

1. FirstOrDefault returns a default — or the fallback you pass.
2. DefaultIfEmpty(0) keeps Average from throwing on empty input.
3. Range and Repeat conjure test sequences from nothing.

Keywords and builtins used here

• int
• string
• var

The run, in numbers

Lines

12

Characters to type

471

Tokens

97

Three-star pace

95 tpm

At the three-star pace of 95 tokens a minute, this run takes about 61 seconds.

Type this snippet

Step 3 of 3 in Materializing & sets, step 15 of 17 in LINQ in depth.

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