Pattern matching

Mon, 24 Oct 2022 14:50:08 +0200

Pattern matching is used for:

testing expression to check if some value have certain characteristics
safer compare because ‘==’ and ‘!=’ can be overloaded

Examples:

a is int number

sequence is IList<T> list

switch statement:

command switch
{
 Operation.SystemTest => RunDiagnostics(),
 Operation.Start => StartSystem(),
 Operation.Stop => StopSystem(),
 Operation.Reset => ResetToReady(),
 _ => throw new ArgumentException("Invalid enum value for command", nameof(command)),
};

switch with ranges:

tempInFahrenheit switch
{
 (> 32) and (< 212) => "liquid",
 < 32 => "solid",
 > 212 => "gas",
 32 => "solid/liquid transition",
 212 => "liquid / gas transition",
};

collection pattern matching:

array is [1,1,2,3,5,8, ..]

Further read:

https://learn.microsoft.com/en-us/dotnet/csharp/fundamentals/functional/pattern-matching

C# on InternetException

Pattern matching