Multi-tier applications using L2S, WCF and Base Class
- by Gena Verdel
Hi all.
One day I decided to build this nice multi-tier application using L2S and WCF.
The simplified model is : DataBase-L2S-Wrapper(DTO)-Client Application.
The communication between Client and Database is achieved by using Data Transfer Objects which contain entity objects as their properties.
abstract public class BaseObject
{
public virtual IccSystem.iccObjectTypes ObjectICC_Type
{
get { return IccSystem.iccObjectTypes.unknownType; }
}
[global::System.Data.Linq.Mapping.ColumnAttribute(Storage = "_ID", AutoSync = AutoSync.OnInsert, DbType = "BigInt NOT NULL IDENTITY", IsPrimaryKey = true, IsDbGenerated = true)]
[global::System.Runtime.Serialization.DataMemberAttribute(Order = 1)]
public virtual long ID
{
//get;
//set;
get
{
return _ID;
}
set
{
_ID = value;
}
}
}
[DataContract]
public class BaseObjectWrapper<T> where T : BaseObject
{
#region Fields
private T _DBObject;
#endregion
#region Properties
[DataMember]
public T Entity
{
get { return _DBObject; }
set { _DBObject = value; }
}
#endregion
}
Pretty simple, isn't it?. Here's the catch. Each one of the mapped classes contains ID property itself so I decided to override it like this
[global::System.Data.Linq.Mapping.TableAttribute(Name="dbo.Divisions")]
[global::System.Runtime.Serialization.DataContractAttribute()]
public partial class Division : INotifyPropertyChanging, INotifyPropertyChanged
{
[global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_ID", AutoSync=AutoSync.OnInsert, DbType="BigInt NOT NULL IDENTITY", IsPrimaryKey=true, IsDbGenerated=true)]
[global::System.Runtime.Serialization.DataMemberAttribute(Order=1)]
public override long ID
{
get
{
return this._ID;
}
set
{
if ((this._ID != value))
{
this.OnIDChanging(value);
this.SendPropertyChanging();
this._ID = value;
this.SendPropertyChanged("ID");
this.OnIDChanged();
}
}
}
}
Wrapper for division is pretty straightforward as well:
public class DivisionWrapper : BaseObjectWrapper<Division>
{
}
It worked pretty well as long as I kept ID values at mapped class and its BaseObject class the same(that's not very good approach, I know, but still) but then this happened:
private CentralDC _dc;
public bool UpdateDivision(ref DivisionWrapper division)
{
DivisionWrapper tempWrapper = division;
if (division.Entity == null)
{
return false;
}
try
{
Table<Division> table = _dc.Divisions;
var q = table.Where(o => o.ID == tempWrapper.Entity.ID);
if (q.Count() == 0)
{
division.Entity._errorMessage = "Unable to locate entity with id " + division.Entity.ID.ToString();
return false;
}
var realEntity = q.First();
realEntity = division.Entity;
_dc.SubmitChanges();
return true;
}
catch (Exception ex)
{
division.Entity._errorMessage = ex.Message;
return false;
}
}
When trying to enumerate over the in-memory query the following exception occurred:
Class member BaseObject.ID is unmapped.
Although I'm stating the type and overriding the ID property L2S fails to work.
Any suggestions?
