Question

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!

Answer 1

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!