Entity Framework 5: Using DatabaseGeneratedOption.Computed option

Question

I have an EF5 code first project that uses the `[DatabaseGenerated(DatabaseGeneratedOption.Computed)]` attribute. This option is overriding my settings. Consider this SQL table: ``` CREATE TABLE Vehicle ( VehicleId int identity(1,1) not null, Name varchar(100) not null default ('Not Set') ) ``` I am using the SQL default construct to set the [Name] is case it is not set. In code behind, I have a class defined similar to: ``` public class Vehicle { ... [DatabaseGenerated(DatabaseGeneratedOption.Computed)] public string ShoulderYN { get; set; } } ``` When I update the entity in code, the value set in the default overrides my new setting. In code, I have (pseudo): ``` vehicle.Name = 'Update Name of Vehicle'; _dbContext.Update(vehicle); _dbContext.SaveChanges(); ``` The expected result is `Vehicle.Name = 'Update Name of Vehicle'`. The actual result is `Vehicle.Name = 'Not Set'`. Is there a way in EF5 to say: if Vehicle.Name is null/empty, use the value defined in the database? Otherwise,…

Accepted Answer

Apparently, no there isn't. It's not that smart :)

As you may already read, Computed option just tells the EF not to update your column, because you will compute a value on the DB-side yourself. EF will then just return newly computed value from your database (which in your case is "Not Set").

Your basic three options are - as per EF Source code documentation:

- None - The database does not generate values.

- Identity - The database generates a value when a row is inserted.

- Computed - The database generates a value when a row is inserted or updated.

https://github.com/aspnet/EntityFramework6/blob/527ae18fe23f7649712e9461de0c90ed67c3dca9/src/EntityFramework/DataAnnotations/Schema/DatabaseGeneratedOption.cs

Since you expect a little more custom logic to be done, I'm afraid you would have to do it yourself. I would suggest you stop relying on database default constraint and do everything in code first approach. This way you would have a code like that:

```
public class Vehicle
{
  public Vehicle()
  {
    this.Name = "Not set";
  }
  
  // Without 'Generated' attribute
  public string Name { get; set; }
}
```

This way, when your Entity is created, it automatically starts with expected default value. And can be later changed by simply modifying the Name property.

Hope it helps!

Entity Framework 5: Using DatabaseGeneratedOption.Computed option

Solution

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