Is it possible in LINQ to SQL to create a computed column using DataContext.CreateDatabase?

Question

I want to dynamically create a database using my DataContext's CreateDatabase Method. I have manually created mapping classes and tested them. But as soon as I add the Expression Column (see below) the creation fails with an SqlCeException and I am unable to find out the exact reason.

    /// <summary>
    /// The sum of ratings for this document.
    /// </summary>
    [Column]
    public Nullable<float> RatingSum { get; set; }

    /// <summary>
    /// The number of times the document was rated.
    /// </summary>
    [Column]
    public Nullable<float> RatingCount { get; set; }

    /// <summary>
    /// Average rating as calculated from RatingSum and RatingCount
    /// </summary>
    [Column(AutoSync=AutoSync.Never, IsDbGenerated=true, Expression = "RatingSum * RatingCount", DbType="REAL")]
    public Nullable<float> Rating { get; set; }

Omitting DbType or changing it to FLOAT didn't help, AutoSync.Always doesn't help either, omitting AutoSync and IsDbGenerated attributes doesn't work either. What am I doing wrong? Or is this simply not supported for a dynamically created db?