Why can't I pull a ushort from a System.Object and then cast it as a uint? (C#)

Question

I'm manipulating the items in a list that's a `System.Management.ManagementObjectCollection`. Each of these items is a `System.Management.ManagementObject` which contains properties indexed by string. See: ``` foreach (ManagementObject queryObj in searcher.Get()) { string osversion = (string)queryObj["Version"]; string os = (string)queryObj["Name"]; uint spmajor = (uint)queryObj["ServicePackMajorVersion"]; uint spminor = (uint)queryObj["ServicePackMinorVersion"]; ... ... ... } ``` Each "dictionary access" to `queryObj` returns a C# `object` which is in fact whatever the property is supposed to be -- I have to know their "real" type beforehand, and that's OK. Problem is, I get a `InvalidCastException` in the `uint` casts. I have to use the real type, which is `ushort`. Shouldn't a cast from `ushort` to `uint` be acceptable and obvious? In this case, I'll eventually convert the values to `string`, but what if I had to get them into `uint` or `int` or `long` variables?

Accepted Answer

You're attempting to unbox a ushort, and it can only be unboxed to a ushort.

Once you've unboxed it you can then cast it as normal.

Any boxed value of type T can only be unboxed to a T (or a Nullable).

Eric Lippert did a very good blog post about this exact thing here.

Why can't I pull a ushort from a System.Object and then cast it as a uint? (C#)

Solution

Problem