I'm just in the process of evaluating XPO for a project and have a few questions I hope can be answered.  Let me first say that at a glance XPO looks very good.  It's pretty simple and cuts out a good deal of the backend grunt work.

1/ I have to work against a legacy data source that does not use identy type columns, but rather alpha fields (e.g. NGR001). XPO appears to insist on having an autogenerated PK.  This would be fine, but I also need to make sure that the legacy PK remains unique.  Is there a "unique" attribute that can be applied to an object's property? Or is there another standard method of managing this type of scenario?

2/ What is the standard method of dealing with inheritance across fairly divergent objects? I have a few properties that are standard for all my objects (e.g. LastUser, LastEditDate, etc.)  If I create a super class that inherits from XPObject and then inherit from my super class for all my other objects, XPO wants to create a table for the super class and then sub tables with a one-to-one relation to it.  This might be fine, but its problematic given my first question, and you end up adding alot of extra data baggage by querying against what will end up being a rather large table.

3/ I've noted there is no "IsDirty" property on the XPObject class.  I can only assume that when the session.Save() or xpobject.Save() are called that the XPObject is only processing those objects that have actually changed. 

Thanks,

Mark 

 

Hi Mark,

Mark Gemmill:

XPO appears to insist on having an autogenerated PK.

Yes, this is the right way of using XPO if you start with a new design.

However, when working with a legacy DB where tables have string IDs, you can use XPLiteObjects instead of XPObjects. Within XPLightObjects, you can define a string field as the key and set its value as you wish.

 public class StringKeyObject : XPLiteObject {
  string id;
  [Key, Size(10)]
  public string Id {
   get { return id; }
   set { SetPropertyValue("Id", ref id, value); }
  }
  public StringKeyObject(Session session) : base(session) { }
  public StringKeyObject() : base(Session.DefaultSession) { }
 }

Regards,

Marc Greiner - DX Squad

"3/ I've noted there is no "IsDirty" property on the XPObject class "

public class MyObject : XPObject {
    public bool IsDirty { get { return this.Session.IsObjectToSave(this) || this.Session.IsNewObject(this);  } }
}

check this out.

 

p.s. you should use UnitOfWork or must be in a Transaction for this to work.

 

 

 

On Tue, 10 Jul 2007 06:50:48 +0000 (UTC), "Mark Gemmill" <> wrote:

>2/ What is the standard method of dealing with inheritance across fairly divergent objects? I have a few properties that are standard for all my objects (e.g. LastUser, LastEditDate, etc.) If I create a super class that inherits from XPObject and then inherit from my super class for all my other objects, XPO wants to create a table for the super class and then sub tables with a one-to-one relation to it. This might be fine, but its problematic given my first question, and you end up adding alot of extra data baggage by querying against what will end up being a rather large table.

I don't have the code in front of me and I can't remember for sure, but I had
this issue before and was able to solve it.

I believe if you mark the intermediate type as NonPersistent no table will be
created for it and all the persistent fields will show up in the table related
to the descendant type. (Or it could have been that marking the intermediate
table as MustInherit did the trick.)

One or the other, but there is a way to do it. I would try NonPersistent
first.

David Shannon

do you mean like this?

 

using System;
using DevExpress.Xpo;
using DevExpress.Xpo.DB;
using DevExpress.Data.Filtering;

namespace Model
{
    [NonPersistent]
    public partial class TBase : XPObject
    {
        public TBase()
        {                       
        }

        public TBase(Session session)
            : base(session)
        {                       
        }

        [DisplayName("GUID")]       
        public Guid? P_GUID
        {
            get { return (Guid?)GetPropertyValue("P_GUID"); }
            set { SetPropertyValue("P_GUID", value); }
        }

        [DisplayName("Replicate")]
        [NullValue(false)]
        public bool? P_MustReplicate
        {
            get { return (bool?)GetPropertyValue("P_MustReplicate"); }
            set { SetPropertyValue("P_MustReplicate", value); }
        }

        [DisplayName("Updated")]
        public DateTime? P_Updated
        {
            get { return (DateTime?)GetPropertyValue("P_Updated"); }
            set { SetPropertyValue("P_Updated", value); }
        }

        [DisplayName("Created")]
        public DateTime? P_Created
        {
            get { return (DateTime?)GetPropertyValue("P_Created"); }
            set { SetPropertyValue("P_Created", value); }
        }
    }
}

Yes, you're right.  Here's my code.  This created just the one table in the database.  Thanks for the input.

 

namespace DevExpressXPO {

using System;using DevExpress.Xpo;

 

[NonPersistent()]

public class SunBaseObject : XPObject {#region << Constructors >>

public SunBaseObject() {}public SunBaseObject(Session session)

:

base(session) { }

#endregion

#region << Fields >>

private string _LocationId;public string LocationId

{

get { return _LocationId; }set { _LocationId = value; }

}

private DateTime _CreationDate;public DateTime CreationDate

{

get { return _CreationDate; }set { _CreationDate = value; }

}

private DateTime _LastEditDate;public DateTime LastEditDate

{

get { return _LastEditDate; }set { _LastEditDate = value; }

}

private string _LastUserId;public string LastUserId

{

get { return _LastUserId; }set { _LastUserId = value; }

}

public bool IsDirty

{

get { return this.Session.IsObjectToSave(this) || this.Session.IsNewObject(this); }

}

#endregion

}

 

public class Customer : SunBaseObject {

 

#region << Fields >>

private string _CustomerId;public string CustomerId

{

get { return _CustomerId; }set { SetPropertyValue<string>("CustomerId",ref _CustomerId, value);}

}

private string _CustomerName;public string CustomerName

{

get { return _CustomerName; }

set { SetPropertyValue<string>("CustomerName",ref _CustomerName, value);}

}

#endregion

 

#region << Constructor >>public Customer(): base() { }

 

public Customer(Session session) : base(session){}

#endregion

 

}

}

de nada...

On Wed, 11 Jul 2007 02:29:01 +0000 (UTC), "Mark Gemmill" <> wrote:

>Yes, you're right. Here's my code. This created just the one table in the database. Thanks for the input.
>

David Shannon:

de nada...

On Wed, 11 Jul 2007 02:29:01 +0000 (UTC), "Mark Gemmill" <> wrote:

>Yes, you're right. Here's my code. This created just the one table in the database. Thanks for the input.
>

 

 

que? 

Que no?

On Wed, 11 Jul 2007 11:13:37 +0000 (UTC), "Rollie Claro" <> wrote:

>que?

muchias gracias