How to test whether a value is boxed in C# / .NET?

Question

I\'m looking for a way to write code that tests whether a value is boxed.

My preliminary investigations indicate that .NET goes out of its way to conceal the fact,

Answer 1

Similar to Allon's answer, but should return the correct answer for any type without generating a compile-time error:

int i = 123;
Console.WriteLine(IsBoxed(i));    // false

object o = 123;
Console.WriteLine(IsBoxed(o));    // true

IComparable c = 123;
Console.WriteLine(IsBoxed(c));    // true

ValueType v = 123;
Console.WriteLine(IsBoxed(v));    // true

int? n1 = 123;
Console.WriteLine(IsBoxed(n1));    // false
int? n2 = null;
Console.WriteLine(IsBoxed(n2));    // false

string s1 = "foo";
Console.WriteLine(IsBoxed(s1));    // false
string s2 = null;
Console.WriteLine(IsBoxed(s2));    // false

// ...

public static bool IsBoxed(T item)
{
    return (item != null) && (default(T) == null) && item.GetType().IsValueType;
}

public static bool IsBoxed(T? item) where T : struct
{
    return false;
}

(Although you could make the argument that the possible compile-time error caused by Allon's code is a feature, not a bug: if you hit a compile-time error then you're definitely not dealing with an unboxed value type!)