Pattern matching · Code-Sage

C# language feature:

Pattern matching

applies to

switch statement, is expressions

benefit

Allows testing for pattern/type and extracting as type.

how to use

1) In is statement, insert type after is followed by variable identifier, use variable in statement as desired.
2) In switch statement, insert type after case followed by variable identifier, use variable in case statement as desired.

example:

        void Is_Pattern_Matching_Example(object object2check)
        {
            if (object2check is int i || (object2check is string s && int.TryParse(s, out i)))
                System.Console.WriteLine($"the int is {i}");
            else
                System.Console.WriteLine("not an int or parsable string");
        }
        void Switch_Pattern_Matching_Example(object object2check)
        {
            switch (object2check)
            {
                case int i:
                    System.Console.WriteLine($"object is an integer with value {i}");
                    break;
                case string s:
                    System.Console.WriteLine($"object is a string ({s}) and has {s.Length} character(s)");
                    break;
                default:
                    System.Console.WriteLine("object is something other than int or string");
                    break;
                case null:
                    System.Console.WriteLine("object is null");
                    break;
            }
        }

C# articles

csharp v2 +

Anonymous methods * Co- and Contra-variance for delegates * Delegate inference * Generics * Getter and setter separate accessibility * Iterators * Method group conversions (delegates) * Nullable types * Partials * Static classes *

csharp v3 +

Anonymous types * Auto-Implemented properties * Expression trees * Extension methods * Implicitly typed local variables * Lambda expression * Object and collection initializers * Partial methods * Query expressions *

csharp v4 +

Generic co- and contravariance * Named and optional arguments *

csharp v5 +

Asynchronous methods * Caller info attributes *

csharp v6 +

A note for CSharp 6 and beyond * Allow await in catch and finally blocks * Auto property initializers * Default values for Read-only Auto-properties * Dictionary (index) initializers * Exception filters * Expression-bodied members * Import of static type members into namespace * Null propagator (null-conditional operator, succinct null checking) * String interpolation * nameof operator *

csharp v7 +

Binary literals * Deconstruction * Digit separators * Expression bodied constructors and finalizers * Expression bodied getters and setters * Generalized async return types * Local functions * Out variables * Pattern matching * Ref returns and locals * Tuples *