Bits of .NET

Checking list contents with if statements is verbose. C# 11 list patterns make it clean.

Traditional Way:

if (numbers.Count >= 3 && numbers[0] == 1 && numbers[2] == 3)
{
    // Do something
}

List Pattern:

if (numbers is [1, _, 3, ..])
{
    // Matches list starting with 1, any value, then 3, then anything
}

// _ = any single element
// .. = zero or more elements

More Examples:

// Exactly 3 elements
if (list is [var first, var second, var third]) { }

// At least 2 elements
if (list is [var first, var second, ..]) { }

// Starts with 1, ends with 5
if (list is [1, .., 5]) { }

// Empty list
if (list is []) { }

// Single element
if (list is [var only]) { }

// Two elements
if (list is [var first, var second]) { }

In Switch:

var message = numbers switch
{
    [] => "Empty",
    [var x] => $"Single: {x}",
    [var x, var y] => $"Pair: {x}, {y}",
    [1, .., 5] => "Starts 1, ends 5",
    _ => "Other"
};

Pattern matching for collections!