UpdateModel requires properties

I was working on a feature at work this week on a ASP MVC project. I was attempting to use UpdateModel to update an object retrieved from the database with values from the POST. If you aren't familiar with it, ASP MVC has a "magic method" to map these POST values to an object. One simply needs to call

UpdateModel(myObjectFromDatabase);

and the new values will be changed on the object. That is all fine and dandy unless it doesn't work. I had checked everything. I could verify that the values were in the Request header. I could verify that UpdateModel was called and did not fail. The values simply were not updated. I finally found the key (thanks to my supervisor). The object I was updating had a mix of auto-properties and fields. Apparently, UpdateModel will only update properties. A quick change from a field to an auto-property and everything worked as it should. Thanks Aaron!