DevForce Community Forum : Error : Null Entity cannot be modified

Error : Null Entity cannot be modified : Figured out what the problem was....

Tue, 05 Feb 2008 16:32:25 -700

Author: JulianBenjamin
Subject: 673
Posted: 05-Feb-2008 at 4:32pm

Figured out what the problem was. I was using two different PersistenceManagers, one to retrieve the data, and the other to save the data.

Error : Null Entity cannot be modified : But it's not a NullEntity,...

Tue, 05 Feb 2008 11:46:21 -700

Author: JulianBenjamin
Subject: 673
Posted: 05-Feb-2008 at 11:46am

But it's not a NullEntity, because that record actually exists in the database.

Error : Null Entity cannot be modified : You need to use UpdateNullEntity()....

Tue, 05 Feb 2008 09:43:13 -700

Author: davidklitzke
Subject: 673
Posted: 05-Feb-2008 at 9:43am

You need to use UpdateNullEntity().

The DevForce Developer's Guide says this:

The null entity cannot be changed, deleted, or saved. But the savvy developer can redefine a null entity‟s default property responses by overriding the UpdateNullEntity() method in the entity‟s Developer class. She could change the Address.City property, for example, so that it returns the string "".

See this tutorial if you want an example:

Edited by davidklitzke - 05-Feb-2008 at 9:44am

Error : Null Entity cannot be modified : I'm getting the following...

Tue, 05 Feb 2008 06:35:15 -700

Author: JulianBenjamin
Subject: 673
Posted: 05-Feb-2008 at 6:35am

I'm getting the following error when setting a value of a related entity.

I have a ItemData entity, and it's related ProductDescription record (joined via ItemNumber in the Entity Relations tab).

When I retrieve the ItemData record, I can use ItemData.ProductDescription.ItemText and get the value, as the record exists in the ProductDescription table. However, when saving the data, I'm assigning a value to the ItemText field in the ItemData.ProductDescription object using ItemData.ProductDescription.ItemText = x and I get a Null Entity Cannot be modified error.

Any ideas? I've pasted the exception below.

IdeaBlade.Util.IdeaBladeException was unhandled by user code
Message="Null entity cannot be modified"
Source="IdeaBlade.Persistence"
StackTrace:
       at IdeaBlade.Persistence.EntityTable.OnColumnChanging(DataColumnChangeEventArgs pArgs)
       at System.Data.DataRow.set_Item(DataColumn column, Object value)
       at IdeaBlade.Persistence.Entity.SetColumnValue(DataColumn pSetColumn, Object pValue)
       at ComNET.Data.ProductDescriptionDataRow.SetItemTextImpl(String value) in D:\code\CatalogManager\CatalogManager.Data\ComNET.Data\ProductDescriptionDataRow.cs:line 488
       at ComNET.Data.ProductDescriptionDataRow.set_ItemText(String value) in D:\code\CatalogManager\CatalogManager.Data\ComNET.Data\ProductDescriptionDataRow.cs:line 480
       at CatalogManager.ItemDetail.btnSave_Click(Object sender, EventArgs e) in D:\code\CatalogManager\CatalogManager\ItemDetail.aspx.cs:line 211
       at DevExpress.Web.ASPxEditors.ASPxButton.OnClick(EventArgs e)
       at DevExpress.Web.ASPxEditors.ASPxButton.RaisePostBackEvent(String eventArgument)
       at DevExpress.Web.ASPxClasses.ASPxWebControl.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument)
       at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument)
       at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData)
       at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
InnerException: