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C# Feature - Relational patterns

Overview

Section titled “Overview”

Relational patterns let you express numeric or comparable thresholds directly in a pattern match instead of nested comparisons.

Introduced In

Section titled “Introduced In”

C# 9.0 (2020)

Before

Section titled “Before”
if (score >= 90)
{
  return "A";
}

After

Section titled “After”
return score switch
{
  >= 90 => "A",
  >= 80 => "B",
  _ => "C"
};

Annotated Example

Section titled “Annotated Example”
bool isWorkingHours = currentHour is >= 9 and < 18;

Gotchas & Best Practices

Section titled “Gotchas & Best Practices”
  • Relational patterns become more readable when paired with logical patterns such as and.
  • Keep branches ordered from most specific to most general.
Section titled “Related Features”

Version Notes

Section titled “Version Notes”
  • C# 9 added relational and logical pattern combinations.