NHibernate Mapping-By-Code for Optimistic Concurrency using SQL Server timestamp column

Question

I'm using NHibernate 3.3.3.4000 and SQL Server 2012.

I've searched for and not found an example of how to use mapping-by-code (loquacious) to configure optimistic concurrency using a SQL Server timestamp (i.e. rownumber) column.

I also use NHibernate's SchemaExport.Create() method to create the SQL Server database, so the mapping must result in a RowVersion column of type timestamp in the SQL Server table after NHibernate has created the database.

My DTO class is setup like this:

public class TestDto {
  public virtual Guid Id { get; set; }
  public virtual string Name { get; set; }
  public virtual Byte[] RowVersion { get; set; }
}

Here Ayende explains how to setup for optimistic concurrency using XML mapping and a SQL Server timestamp column. My attempts to mimic this using mapping-by-code (shown below) have all failed in one way or another.

http://ayende.com/blog/3946/nhibernate-mapping-concurrency

Here is a mapping-by-code example for optimistic concurrency, but it doesn't use a SQL Server timestamp column - and my attempts to guess at the changes required to make it work with a timestamp column have failed:

http://notherdev.blogspot.com/2012/01/mapping-by-code-concurrency.html

Here is my non-working attempt at mapping-by-code that is based as best as I can determine on the previous two articles:

  public TestMap() {
     Table( "Test" );

     DynamicUpdate( true );

     Id( x => x.Id, map => {
        map.Column( "ID" );
        map.Generator( Generators.GuidComb );
     } );

     Version( x => x.RowVersion, map => {
        map.Column( "RowVersion" );
        map.Generated( VersionGeneration.Always );
        map.UnsavedValue( null );
        map.Insert( true );
        //map.Type( new TimestampType() );       // Creates a datetime (not null) column.
        //map.Type( new BinaryBlobType() );      // Creates a VARBINARY(MAX) (not null) column.
        //map.Access( Accessor.Field );          // Causes error: Could not find property nor field 'RowVersion' in class 'SQC.Repository.Dtos.DataGroupDto'
     } );

     Property( x => x.Name, map => {
        map.Column( "Name" );
        map.NotNullable( true );
     } );
  }

When I uncomment this line the created table has RowVersion as "datetime (not null)" - and I need a SQL Server timestamp type.

map.Type( new TimestampType() );       // Creates a datetime (not null) column.

When I uncomment this line the created table has RowVersion as "VARBINARY(MAX) (not null)" - and I need a SQL Server timestamp type.

map.Type( new BinaryBlobType() );      // Creates a datetime (not null) column.

When I uncomment this line I get this error at runtime "Could not find property nor field 'RowVersion' in class 'TestDto'".

map.Access( Accessor.Field );

I hope someone can explain how to make this work using mapping-by-code (loquacious). The project is heavily committed to mapping-by-code, so Fluent NHibernate is not an option for us.

Dawood Moazzem Dawood Moazzem · Accepted Answer · 2014-09-02T19:33:36

get rid of the "map.Access( Accessor.Field );" This tells nhibernate to use a backing field to work with, however since you are using an auto property, there is no backing field. Either dont have it, or just use Accessor.Proper

NHibernate Mapping-By-Code for Optimistic Concurrency using SQL Server timestamp column

1 Answers