How can I map a UInt64 field to a decimal(20, 0) column using Fluent nHibernate?

Question

I'm using

MS SQL Server 2008R2
Fluent nHibernate 1.3
nHibernate 3.2

I have a UInt64 field in my domain that potentially takes up the entire UInt64 range. Since MS-SQL doesn't support unsigned integers we decided to store it in a decimal(20,0) column (at least for now). I've tried using CustomSqlType("decimal(20, 0)") on that column in my mappings but I'm still getting an error when I try to access that field that says the database doesn't support UInt64.

I've tried

CustomSqlType("Decimal").Precision(20).Scale(0)
CustomSqlType("decimal(20, 0)")
CustomType() and the permutations of CustomSqlType and CustomType.

Edit The error it gives is "No mapping exists from DbType UInt64 to a known SqlDbType."

Edit 2 This works for the write side but breaks with an Invalid cast when values are read back out

.CustomSqlType("decimal").Precision(20).Scale(0)
.CustomType<NHibernate.Type.DoubleType>()

Firo Firo · Accepted Answer · 2011-09-20T11:40:11

i would go with a user type

class UInt64UserType : ImmutableUserType
{
    public object NullSafeGet(IDataReader rs, string[] names, object owner)
    {
        var value = NHibernateUtil.Decimal.NullSafeGet(rs, names[0]);
        return (value == null) ? 0 : Convert.ToUInt64(value);
    }

    public void NullSafeSet(IDbCommand cmd, object value, int index)
    {
        decimal d = Convert.ToDecimal(value);
        NHibernateUtil.Decimal.NullSafeSet(cmd, d, index);
    }

    public Type ReturnedType
    {
        get { return typeof(UInt64); }
    }

    public SqlType[] SqlTypes
    {
        get { return new[] { SqlTypeFactory.Decimal }; }
    }
}


.CustomType<UInt64UserType>()

Edit: sorry forgot to note. i have a lot of usertypes so i implemented my own baseclasses

public abstract class ImmutableUserType : UserTypeBase
{
    public override bool IsMutable
    {
        get { return false; }
    }

    public override object DeepCopy(object value)
    {
        return value;
    }

    public override object Replace(object original, object target, object owner)
    {
        return original;
    }

    public override object Assemble(object cached, object owner)
    {
        return cached;
    }

    public override object Disassemble(object value)
    {
        return value;
    }
}

public abstract class UserTypeBase : IUserType
{
    public new virtual bool Equals(object x, object y)
    {
        return EqualsHelper.Equals(x, y);
    }

    public virtual int GetHashCode(object x)
    {
        return (x == null) ? 0 : x.GetHashCode();
    }

    public abstract object Assemble(object cached, object owner);

    public abstract object DeepCopy(object value);

    public abstract object Disassemble(object value);

    public abstract bool IsMutable { get; }

    public abstract object NullSafeGet(System.Data.IDataReader rs, string[] names, object owner);

    public abstract void NullSafeSet(System.Data.IDbCommand cmd, object value, int index);

    public abstract object Replace(object original, object target, object owner);

    public abstract Type ReturnedType { get; }

    public abstract SqlType[] SqlTypes { get; }
}

How can I map a UInt64 field to a decimal(20, 0) column using Fluent nHibernate?

1 Answers