Updating the Entity Framework Partial Entity

I am using Asp.net Webapi and EF and I am having problems with partial updates with Entity Framework 5.

I usually get 20 fields from REST services that I need to update from a full entity. When I update, I am setting the state of the Modified entity. The entire object is updated all the time, overriding any existing values ​​in the table that should not be changed as a result of the update.

There are random fields I got from REST services, but not fixed fields that can help me determine which properties are being updated.

I want to know how this problem is solved there and what methods are used to fix it.

Thank.