Computed column based on rows from another table

Question

I have the following (simplified) table

public class Door
{
    public int Id { get; set; }
    public bool Locked { get; set; }
}

Now the problem with this table is that I don't know how long the door has been locked or not. I could add a new DateTime column, but then, if the door was locked, opened and locked again, I wouldn't know exactly when it was locked the first time since that would be overwritten. So I added a new table

public class Locks
{
    public int Id { get; set; }
    public int DoorId { get; set; }
    public virtual Door Door { get; set; }
    public DateTime? LockedFrom { get; set; }
    public DateTime? LockedTo { get; set; }
}

and added a public Collection<Locks> to my Door table. This is all nice and good and would solve my first problem. However, Door and Door.Locked has been used extensively throughout our code and changing all those queries would be a very large job. So my hope was that I could rewrite Door.Locked to be a computed column. It should collect the entries for that Door from Locks and compare their DateTimes to the current time to find out if the door is locked right now. It is important that this is a computed column (handled on server side) and not a function or calculated parameter in the entity, since that would cause all queries that filters on Door.Locked to be handled in memory (and I have maaany Doors in my db). I would also prefer if Door.Locked could be not nullable, to avoid changing its type to Bool?, and this seems to be possible by making the column persisted. I've seen examples of computed columns in .NET Core where they use entityTypeBuilder.Property(x => x.Locked).HasComputedColumnSql("some sql formula"), but none that do this when the formula depends upon the content of another table.

Conclusion: I want to create a computed column code first that calculates its value using the content of another table.

Thank you!