Fluent NHibernate - Data Annotation Conventions

PropertyConvention.cs

namespace YourProjectName.Here.NHibernateMaps.Conventions
{
    using System;
    using System.ComponentModel.DataAnnotations;
    using System.Linq;

    using DataAnnotationsExtensions;

    using FluentNHibernate.Conventions.Instances;

    public class PropertyConvention : FluentNHibernate.Conventions.IPropertyConvention
    {
        public void Apply(IPropertyInstance instance)
        {
            if (instance == null) return;

            // bracket every property to ensure resevered work problems go away.
            instance.Column(string.Format("[{0}]", instance.Name));

            instance.Access.CamelCaseField();

            if (instance.Type == typeof(string))
            {
                ProcessStringTypes(instance);
            }

            if (instance.Type == typeof(DateTime))
            {
                ProcessDateTypes(instance);
            }
        }

        private static void ProcessDateTypes(IPropertyInstance instance)
        {
            if (instance == null) return;

            HasNullAttribute(instance);

            if (instance.Name.ToUpper().Contains("START") || instance.Name.ToUpper().Contains("CREATEDON"))
            {
                instance.Default("(getdate())");
                instance.Not.Nullable();
            }
        }

        private static void ProcessStringTypes(IPropertyInstance instance)
        {
            if (instance == null) return;

            HasKeyAttribute(instance);

            HasNullAttribute(instance);

            var max = HasMaxAttributes(instance);

            if (max > 0)
            {
                instance.CustomSqlType(string.Format("varchar({0})", max));
                return;
            }

            max = HasLengthAttributes(instance);

            if (max > 0)
            {
                instance.CustomSqlType(string.Format("varchar({0})", max));
                return;
            }

            ConventionBasedLengthAssignment(instance);
        }

        private static void ConventionBasedLengthAssignment(IPropertyInstance instance)
        {
            if (instance == null) return;

            if (instance.Name.ToUpper().Contains("SHORT"))
            {
                instance.CustomSqlType("varchar(10)");
                return;
            }

            switch (instance.Name)
            {
                case "Name":
                    instance.CustomSqlType("varchar(50)");
                    break;
                case "Description":
                    instance.CustomSqlType("varchar(150)");
                    break;
                default:
                    instance.CustomSqlType("varchar(255)");
                    break;
            }
        }

        private static void HasNullAttribute(IPropertyInstance instance)
        {
            if (instance == null) return;

            if (instance.Property.MemberInfo.IsDefined(typeof(RequiredAttribute), false))
            {
                instance.Not.Nullable();
            }
        }

        private static long HasLengthAttributes(IPropertyInstance instance)
        {
            if (instance == null) return 0;

            return (from attribute
                        in instance.Property.MemberInfo.GetCustomAttributes(typeof(StringLengthAttribute), false)
                    select (StringLengthAttribute)attribute into result
                    select result.MaximumLength).FirstOrDefault();
        }

        private static void HasKeyAttribute(IPropertyInstance instance)
        {
            if (instance == null) return;

            if (instance.Property.MemberInfo.IsDefined(typeof(KeyAttribute), false))
            {
                instance.Unique();
            }
        }

        private static long HasMaxAttributes(IPropertyInstance instance)
        {
            if (instance == null) return 0;

            var me = (from attribute
                        in instance.Property.MemberInfo.GetCustomAttributes(typeof(MaxAttribute), false)
                    select (MaxAttribute)attribute into result
                    select result.Max).FirstOrDefault();

            long length = 0;

            if (me != null && long.TryParse(me.ToString(), out length))
            {
                return length;
            }

            return 0;
        }
    }
}