Calculated column in EF Code First

Question

I need to have one column in my database calculated by database as (sum of rows) - (sum of rowsb). I\'m using code-first model to create my database.

Here is what I

Answer 1

You can create computed columns in your database tables. In the EF model you just annotate the corresponding properties with the DatabaseGenerated attribute:

[DatabaseGenerated(DatabaseGeneratedOption.Computed)]
public double Summ { get; private set; } 

Or with fluent mapping:

modelBuilder.Entity().Property(t => t.Summ)
    .HasDatabaseGeneratedOption(DatabaseGeneratedOption.Computed)

As suggested by Matija Grcic and in a comment, it's a good idea to make the property private set, because you'd probably never want to set it in application code. Entity Framework has no problems with private setters.

Note: For EF .NET Core you should to use ValueGeneratedOnAddOrUpdate because HasDatabaseGeneratedOption doesnt exists, e.g.:

modelBuilder.Entity().Property(t => t.Summ)
    .ValueGeneratedOnAddOrUpdate()