NHibernate nvarchar/ntext truncation problem

I'm using nhibernate to store some user settings for an app in a SQL Server Compact Edition table.

This is an excerpt the mapping file:

<property name="Name" type="string" />
<property name="Value" type="string" />

Name is a regular string/nvarchar(50), and Value is set as ntext in the DB

I'm trying to write a large amount of xml to the "Value" property. I get an exception every time:

@p1 : String truncation: max=4000, len=35287, value='<lots of xml..../>'

I've googled it quite a bit, and tried a number of different mapping configurations:

<property name="Name" type="string" />
<property name="Value" type="string" >
  <column name="Value" sql-type="StringClob" />
</property>

That's one example. Other configurations include "ntext" instead of "StringClob". Those configurations that don't throw mapping exceptions still throw the string truncation exception.

Is this a problem ("feature") with SQL CE? Is it possible to put more than 4000 characters into a SQL CE database with nhibernate? If so, can anyone tell me how?

Many thanks!

Solution

Okay, with many thanks to Artur in this thread, here's the solution: Inherit from the SqlServerCeDriver with a new one, and override the InitializeParamter method:

using System.Data;
using System.Data.SqlServerCe;
using NHibernate.Driver;
using NHibernate.SqlTypes;

namespace MySqlServerCeDriverNamespace
{
    /// <summary>
    /// Overridden Nhibernate SQL CE Driver,
    /// so that ntext fields are not truncated at 4000 characters
    /// </summary>
    public class MySqlServerCeDriver : SqlServerCeDriver
    {
        protected override void InitializeParameter(
            IDbDataParameter dbParam,
            string name,
            SqlType sqlType)
        {
            base.InitializeParameter(dbParam, name, sqlType);

            if (sqlType is StringClobSqlType)
            {
                var parameter = (SqlCeParameter)dbParam;
                parameter.SqlDbType = SqlDbType.NText;
            }

        }
    }
}

Then, use this driver instead of NHibernate's in your app.config

<nhibernateDriver>MySqlServerCeDriverNamespace.MySqlServerCeDriver , MySqlServerCeDriverNamespace</nhibernateDriver>

I saw a lot of other posts where people had this problem, and solved it by just changing the sql-type attribute to "StringClob" - as attempted in this thread.

I'm not sure why it wouldn't work for me, but I suspect it is the fact that I'm using SQL CE and not some other DB. But, there you have it!