Non-boxing generic conversions

Boxing.cs

static void Main()
{
	Console.WriteLine(X<int>.GetValue());
	Console.WriteLine(X<long>.GetValue());
}

static class X<T> {
	static int IntValue = 42;
	static long LongValue = 64;
	
	public static T GetValue() {
		// Modify this method to run in O(1) allocations (ie, no boxing)
		
		if (typeof(T) == typeof(int))
			return (T)(object)IntValue;
		else if (typeof(T) == typeof(long))
			return (T)(object)LongValue;
		else
			throw new ArgumentException();
	}	
}

This source is written to be pasted into LINQPad; if you want to use a regular compiler, you'll need to wrap Main() in a class.