Fluent NHibernate.Automapping change data type in Database

Question

I'm new to FluentNHibernate. I am working with AutoMapping. Let's say, I have a database which is generated by NHibernate. There's a table, named Document with 2 columns

• Id: int
• Description: nvarchar(255)

which is mapped to this class

public class Document
{
    public virtual int Id { get; set; }
    public virtual string Description{ get; set; }
}

I want to change data type of Description from nvarchar(255) to text in Database, so I created a console application as follow:

public class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Start process");           

        AutoMap.AssemblyOf<Document>().Override<Document>(y => y.Map(x => x.Description).CustomSqlType("text"));         

        Console.WriteLine("End process");
    }
}

There's no error, but nothing happened, the column Description is still nvarchar(255). I don't know what I am missing here. Any thought appreciated! Thanks

Answer 1

SchemaUpdate can not alter columns only add it. However you could recreate (drop and create) it. Also if you set the length of a text field over a specific threshold (often 8k) then most Drivers will create the equivalent of "text" instead of "varchar".

var config = Fluently.Configure()
    .Database(...)
    .Mappings(m => m.Automapping.Add(AutoMap.AssemblyOf<Document>().Override<Document>(y => y.Map(x => x.Description).Length(20000)))
    .BuildConfiguration();

new SchemaExport(config).Create(true, true);