As far as I am aware, this method doesn't check if an asset is loaded, but it checks if an asset exists and it can be loaded.

If that's the case, would it make sense to add "IsLoaded" to check whether or not an asset was already loaded (exists in loadedAssets)?

I am not sure if this would add much value, as ContentManager ensures that the asset is loaded only once, and repeated Load calls will not load the asset several times.

I'm writing an async version that derives the ContentManager. It would be easy to handle scenarios where I have to add <Type, string> into a queue of assets to be loaded if I could simply do Exists(asset). Not a big deal though.

Maybe it would help more if we would make protected some of private methods in ContentManager? This will allow extensibility, however will not add a confusing IsLoaded method, which doesn't add much value anyway.

The above scenario requires only loadedAssets to be protected. If it's an issue of consistency/conventions, that making all relevant methods protected works too.

I made some members protected in the changeset above, however I am not sure if I fully understood your usage scenario. If these changes are ok - close the issue, otherwise - post a code fragment from which we can understand what you need to achieve.