Fluent NHibernate PK Rename convention (SQL Server)

Following on from my previous post of using some sql to enable the SchemaExport tool to make changes outside of its current capabilities, I created a simple convention for Fluent NHibernate which enables you to name the PK’s of tables.
Currently this only works with SQL Server, but I believe that this approach should also be possible in other databases.

using System.Linq;
using System.Text;
using Iesi.Collections.Generic;
using NHibernate.Dialect;
using NHibernate.Mapping;

namespace Conventions
{
    public class CustomPrimaryKeyIndexNameConvention
    {
        public static void CreateUpdatePkNameScript(NHibernate.Cfg.Configuration config)
        {
            var script = new StringBuilder("");
            script.AppendLine("DECLARE @keyName AS SYSNAME");
            script.AppendLine();
            foreach (var tableName in config.ClassMappings.Select(m => m.Table.Name).Distinct())
            {
                script.AppendFormat(string.Format("SELECT  @keyName = name FROM sys.key_constraints kc WHERE kc.parent_object_id = OBJECT_ID('dbo.{0}', 'U')", tableName));
                script.AppendLine();
                script.AppendFormat("EXEC sp_rename @keyName, N'PK_{0}', N'OBJECT';", tableName);
                script.AppendLine();
            }

            config.AddAuxiliaryDatabaseObject(new SimpleAuxiliaryDatabaseObject(script.ToString(), null, new HashedSet<string> { typeof(MsSql2000Dialect).FullName, typeof(MsSql2005Dialect).FullName, typeof(MsSql2008Dialect).FullName }));
        }
    }
}

As you can see, the convention is to use “PK_<TableName>” for the PK name and is applied using the Auxiliary database extensions:

.ExposeConfiguration(CustomPrimaryKeyIndexNameConvention.CreateUpdatePkNameScript)