Code-first migration: How to set default value for new property?

Question

I am using EF6 for storing instances of the report class in my database. The database already contains data. Say I wanted to add a property to report,

public class report {
    // ... some previous properties

    // ... new property:
    public string newProperty{ get; set; }
}

Now if I go to the package-manager console and execute

add-migration Report-added-newProperty
update-database

I will get a file in the '/Migrations' folder adding a newProperty column to the table. This works fine. However, on the older entries in the database, the value for the newProperty is now an empty string. But I want it to be, e.g., "old".

So my question is: How do I set default values for new properties (of any type) in the migration script (or elsewhere)?

Solution 1

If you see the generated migration code you will see AddColumn

AddColumn("dbo.report", "newProperty", c => c.String(nullable: false));

You can add defaultValue

AddColumn("dbo.report", "newProperty", 
           c => c.String(nullable: false, defaultValue: "old"));

Or add defaultValueSql

AddColumn("dbo.report", "newProperty",
           c => c.String(nullable: false, defaultValueSql: "GETDATE()"));

Solution 2

Hope it helps someone. Putting everything together from previous answers (example using a boolean property):

1) Add a new property to the entity.

/// <summary>
/// Determines if user is enabled or not. Default value is true
/// </summary>
public bool IsEnabled { get; set; }

2) Run the command below to add the new change in the migrations.

add-migration addIsEnabledColumn

3) A migration file is created from the command above, open that file.

4) Set the default value.

public override void Up()
{
        AddColumn(
            "dbo.AspNetUsers", 
            "IsEnabled", 
            c => c.Boolean(
                nullable: false, 
                defaultValue: true
            )
        );
}

Solution 3

You have to change the line in your migration script which adds the the property/column like this:

AddColumn("dbo.reports", "newProperty", c => c.String(nullable: false, defaultValue: "test"));

Comments

[Barry]

Would be nice if it properly pulled in the [DefaultValue(xyz)] attribute as defined in the code first model. Instead of having to remember which columns need what each time you Add-Migration; having to post-edit the generated file, followed by the normal running of the Update-Database against that changed file. I wonder if it's possible to override that unintelligent behavior.... I can't believe no one has improved on this. Surely I'm not the only one frustrated by this with the default AspNet Identity model... LockoutEnabled, EmailConfirmed, AccessFailedCount. all hardcoded, all problems

[Efrain]

This does not seem to work with MySQL-EF. 'defaultValue' doesn't set the value, and 'defaultValueSql' creates an exception ("blob text geometry or json column can't have a default value") ... the only workaround left is to use raw SQL. :(

[chipples]

What's wrong is that it's not actually setting a default value in the database.

[EeKay]

For those that needed default value for an enum just like me: AddColumn("dbo.report", "newEnumProperty", c => c.Int(nullable: false, defaultValue: 0)); //use integer to set default enum value

[vinmm]

5) Run Update-Database after step 4 to update the actual database too with the changes. Adding this point just for the sake of newbies.

[StefanoV]

Quoting @Efrain, with EF Core 5 and MySQL I got empty fields. The default is not applied.

[user1735921]

How to add default value of other column, eg: I want the new property default vaue to be report.OldProperty ?

[Dhir Pratap]

Is it possible to have the default be a function of other fields?