Retrieving values of ReadOnly fields from DynamicData DetailsView in Edit Mode on Updating using LinqDataSource - c#-4.0

Question

I have several tables in my database that have read-only fields that get set on Inserting and Updating, namely: AddDate (DateTime), AddUserName (string), LastModDate (DateTime), LastModUserName (string).
All of the tables that have these values have been set to inherit from the following interface:
public interface IUserTrackTable
{
string AddUserName { get; set; }
DateTime AddDate { get; set; }
string LastModUserName { get; set; }
DateTime LastModDate { get; set; }
}
As such, I have the following method on the Edit.aspx page:
protected void DetailsDataSource_Updating(object sender, LinqDataSourceUpdateEventArgs e)
{
IUserTrackTable newObject = e.NewObject as IUserTrackTable;
if (newObject != null)
{
newObject.LastModUserName = User.Identity.Name;
newObject.LastModDate = DateTime.Now;
}
}
However, by the time it hits this method, the e.OriginalObject has already lost the values for all four fields, so a ChangeConflictException gets thrown during the actual Update. I have tried adding the four column names to the DetailsView1.DataKeyNames array in the Init event handler:
protected void Page_Init(object sender, EventArgs e)
{
// other things happen before this
var readOnlyColumns = table.Columns.Where(c => c.Attributes.SingleOrDefaultOfType<ReadOnlyAttribute>(ReadOnlyAttribute.Default).IsReadOnly).Select(c => c.Name);
DetailsView1.DataKeyNames = DetailsView1.DataKeyNames.Union<string>(readOnlyColumns).ToArray<string>();
DetailsView1.RowsGenerator = new CustomFieldGenerator(table, PageTemplates.Edit, false);
// other things happen after this
}
I've tried making that code only happen on PostBack, and still nothing. I'm at a lose for how to get the values for all of the columns to make the round-trip.
The only thing the CustomFieldGenerator is handling the ReadOnlyAttribute, following the details on C# Bits.
UPDATE: After further investigation, the values make the round trip to the DetailsView_ItemUpdating event. All of the values are present in the e.OldValues dictionary. However, they are lost by the time it gets to the LinqDataSource_Updating event.
Obviously, there are the "solutions" of making those columns not participate in Concurrency Checks or other ways that involve hard-coding, but the ideal solution would dynamically add the appropriate information where needed so that this stays as a Dynamic solution.

Answer 1

i Drovani, I assume you want data auditing (see Steve Sheldon's A Method to Handle Audit Fields in LINQ to SQL), I would do this in the model in EF4 you can do it like this:
partial void OnContextCreated()
{
// Register the handler for the SavingChanges event.
this.SavingChanges += new EventHandler(context_SavingChanges);
}
private static void context_SavingChanges(object sender, EventArgs e)
{
// handle auditing
AuditingHelperUtility.ProcessAuditFields(objects.GetObjectStateEntries(EntityState.Added));
AuditingHelperUtility.ProcessAuditFields(objects.GetObjectStateEntries(EntityState.Modified), InsertMode: false);
}
internal static class AuditingHelperUtility
{
internal static void ProcessAuditFields(IEnumerable<Object> list, bool InsertMode = true)
{
foreach (var item in list)
{
IAuditable entity = item as IAuditable;
if (entity != null)
{
if (InsertMode)
{
entity.InsertedBy = GetUserId();
entity.InsertedOn = DateTime.Now;
}
entity.UpdatedBy = GetUserId();
entity.UpdatedOn = DateTime.Now;
}
}
}
}
Sadly this is not possible with EF v1