patternmatch.cs

//Const pattern check

public static void IsPattern(object o)
{
    if (o is null) Console.WriteLine("it's a const pattern");
    //...
}

public static void IsPattern(object o)
{
    if (o is null) throw new ArgumentNullException(nameof(o));
    if (o is 42) Console.WriteLine("it's 42");
    //...
}

//Type Pattern
if (o is int i) Console.WriteLine($"it's a type pattern 
if (o is Person p) Console.WriteLine($"it's a person: {p.FirstName}");

//var pattern
if (o is var x) Console.WriteLine($"it's a var pattern with the type {x?.GetType()?.Name}");