GWT for C#

Found an interesting project the other day, basically GWT for c#. Except, the cool thing about it is that it does not generate javascript directly from the c#-code (as Script# does), instead it generates javascript the MSIL-bytecode, meaning you can theoretically write in any language that compiles to MSIL (VB.Net, IronPython, Boo). Also, the project states that is should be possible to debug the compiled code inside Visual Studio, something that afaik Script# cannot do.

Here you can find the initial announcement on the Alt.Net yahoo group.

NHibernate enum to char(1)

For a new project we are using NHibernate to implement database persistance. Today I ran into an issue with persisting enum's. By default, NHibernate uses type in the database and the enum's underlying type, in order to generate values. For example a simple enum like this:

public enum CoffeType
{
Sugar,
NoSugar
}

with this mapping file:

<property column="CoffeType" type="Business.Entities.CoffeType, Business.Core" name="CoffeType" null="true">

and a column in the database of type integer means that Sugar becomes 0 and NoSugar becomes 1. This is all fine, and works without problems at all. However, I wanted to use predetermined values for the enums, like this:

public enum CoffeType
{
Sugar = 'S',
NoSugar = 'N'
}

I changed the type in the database from integer to Char(1). This made NHibernate puke when inserting data. After digging into the generated sql-statements, it turned out that NHibernate choose to convert my enum-values into "Sugar" and "NoSugar" instead of 'S' and 'N'. This is probably due to recognizing any Char-type in the database as a String-datatype in .NET, and converting the enum's appropriately.

A few minutes of searching the net turned up the following post:

http://blog.bittercoder.com/CategoryView,category,NHibernate.aspx

.. which solved the exact same problem, with Castle's ActiveRecord instead of NHibernate. It turns out that the solution is called NHibernate User Types. This is what I ended up with in the mapping-file:

<property column="CoffeType" type="Business.Entities.CoffeTypeType, Business.Core" name="CoffeType" null="true" />

and this is the corresponding C#-class:

public class CoffeTypeType : NHibernate.Type.PersistentEnumType
{
    public CoffeTypeType()
        : base(typeof(CoffeType))
    {
    }

    public override object GetValue(object code)
    {
        return Convert.ToChar(code);
    }

    public override object GetInstance(object code)
    {
        return (CoffeType) Enum.ToObject(typeof(CoffeType), (Byte) ((Char) GetValue(code)));
    }

    public override void Set(IDbCommand cmd, object value, int index)
    {
        IDataParameter par = (IDataParameter)cmd.Parameters[index];
        par.DbType = DbType.StringFixedLength;

        if (value == null) {
            par.Value = DBNull.Value;
        }
        else {
            par.Value = GetValue(value);
        }
    }

    public new static SqlType GetUnderlyingSqlType(System.Type enumClass)
    {
        if (Enum.GetUnderlyingType(enumClass).FullName == "System.Char") {
            return NHibernate.SqlTypes.SqlTypeFactory.GetString(1);
        }
        else {
            return NHibernate.Type.PersistentEnumType.GetUnderlyingSqlType(enumClass);
        }
    }
}

This is the way to make NHibernate map an enum property to char(1) database field.