Question

I’ve added the [Required] data annotation to one of my models in an ASP.NET MVC application. After creating a migration, running the Update-Database command results in the following error:

Cannot insert the value NULL into column ‘Director’, table
‘MOVIES_cf7bad808fa94f89afa2e5dae1161e78.dbo.Movies’; column does not
allow nulls. UPDATE fails. The statement has been terminated.

This is due to some records having NULL in their Director columns. How can I automatically change those values to some default (say “John Doe”) director?

Here is my model:

  public class Movie
    {
        public int ID { get; set; }
        [Required]
        public string Title { get; set; }

        [DataType(DataType.Date)]
        public DateTime ReleaseDate { get; set; }

        [Required]
        public string Genre { get; set; }

        [Range(1,100)]
        [DataType(DataType.Currency)]
        public decimal Price { get; set; }

        [StringLength(5)]
        public string Rating { get; set; }

        [Required]     /// <--- NEW
        public string Director { get; set; }
    }

and here is my latest migration:

public partial class AddDataAnnotationsMig : DbMigration
{
    public override void Up()
    {
        AlterColumn("dbo.Movies", "Title", c => c.String(nullable: false));
        AlterColumn("dbo.Movies", "Genre", c => c.String(nullable: false));
        AlterColumn("dbo.Movies", "Rating", c => c.String(maxLength: 5));
        AlterColumn("dbo.Movies", "Director", c => c.String(nullable: false));
    }

    public override void Down()
    {
        AlterColumn("dbo.Movies", "Director", c => c.String());
        AlterColumn("dbo.Movies", "Rating", c => c.String());
        AlterColumn("dbo.Movies", "Genre", c => c.String());
        AlterColumn("dbo.Movies", "Title", c => c.String());
    }
}

Answer 1

If I remember correctly, something like this should work:

AlterColumn("dbo.Movies", "Director", c => c.String(nullable: false, defaultValueSql: "'John Doe'"));

Note: The defaultValueSql parameter value is treated as a verbatim SQL statement, so if the required value is effectively a string, like the John Doe example, then single quotes are required around the value.