Map SQLDecimal property in NHibernate - nhibernate

Question

I'm trying to read a decimal (38,16) from a SQL Server DB and struggling. After much reading around I'm trying to implement a custom type for SQL Decimal with the following code:
public class BigDecimal : IUserType
{
public bool Equals(object x, object y)
{
return object.Equals(x,y);
}
public int GetHashCode(object x)
{
return x.GetHashCode();
}
public object NullSafeGet(IDataReader rs, string[] names, object owner)
{
int index = rs.GetOrdinal(names[0]);
object result = rs.GetValue(index);
return result;
}
public void NullSafeSet(IDbCommand cmd, object value, int index)
{
//Not got here yet
}
public object DeepCopy(object value)
{
return value;
}
public object Replace(object original, object target, object owner)
{
return original;
}
public object Assemble(object cached, object owner)
{
return cached;
}
public object Disassemble(object value)
{
return value;
}
public SqlType[] SqlTypes { get { return new[] {SqlTypeFactory.Decimal}; } }
public Type ReturnedType { get { return typeof (SqlDecimal); } }
public bool IsMutable { get { return false; } }
}
but the output of rs.GetValue is a decimal not at SQLDecimal which causes an OverflowException.
The class looks like this:
public class Billy
{
public BigDecimal TheNumber {get;set;}
}
and the mapping looks like this:
public class BillyMap : ClassMap<Billy>
{
public BillyMap()
{
Map(b=>b.TheNumber).CustomType<BigDecimal>();
}
}
Please can someone tell me where I'm going wrong.

Answer 1

I think you need to cast the reader to SqlDataReader so you can access either GetSqlDecimal() or GetSqlValue(), as GetValue() will convert to a basic .Net Framework type. From 'https://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqldatareader.getsqlvalue%28v=vs.110%29.aspx':
GetSqlValue returns data using the native SQL Server types. To retrieve data using the .NET Framework types, see GetValue.

Answer 2

In the end I made a something which performs a convert in the SQL and made it a Property Part and just use it on all the mapping files:
private const string DECIMAL_CONVERSION = "(CONVERT(decimal(28,6), [{0}]))";
private static string MapDecimalProperty(string fieldName)
{
return string.Format(DECIMAL_CONVERSION, fieldName.Trim('[',']'));
}
public static PropertyPart LongDecimal(this PropertyPart part, string fieldName)
{
return part.Formula(MapDecimalProperty(fieldName));
}
the on the mapping:
Map(ep => ep.BigDecimalField).EDWDecimal("[BigDecimalField]");
this works for now. I've informed the data architecture team that this is happening and they don't think that it will be a problem with any current data and will consider it for future developments.