Type pattern

Context: The type pattern tests whether an expression is of a specified type and, if so, assigns it to a new variable.

object obj = "Hello";
if (obj is string s)
{
    Console.WriteLine(s.Length);
}

With when clause

object obj = 42;
if (obj is int i && i > 10)
{
    Console.WriteLine("Large integer");
}
// Or using when in switch
string result = obj switch
{
    int x when x > 0 => "Positive int",
    int x => "Non-positive int",
    null => "Null",
    _ => "Other"
};

Real-world usage example

Handling different JSON token types: When parsing JSON with System.Text.Json, you can use type pattern to handle JsonValueKind.Number, JsonValueKind.String, etc.

Example: JsonDocument returns JsonElement; you can check ValueKind with type pattern.

Related sections

• 6.5 Pattern matching
• 6.5.1 Constant pattern