/// <summary>
/// Marks a Migration version number as having been rolled back from the database
/// </summary>
/// <param name = "version">The version number of the migration that was removed</param>
public void MigrationUnApplied(long version)
{
CreateSchemaInfoTable();
SchemaInfo.RecordMigrationUnApplied(version);
_appliedMigrations.Remove(version);
}