[dba-VB] CodeFirst, DataBinding and audit trailing deleted items on client side

 Sample code part I:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data.Entity;
using System.Linq;
using System.Windows.Forms;
namespace TestWindowsFormsApplication1
{
public class GenericEntityGridViewHandler<C, T> : IDisposable
where C : DbContext
where T : class 

{
private string _idFieldName;
private string _altKeyFieldName;
private string _dataLoadSql;
public GenericEntityGridViewHandler(
DataGridView entityDataGridView,
BindingSource entityBindingSource,
string dataLoadSql,
string idFieldName = "Id",
string altKeyFieldName = "Name")
{
_entityDataGridView = entityDataGridView;
_entityBindingSource = entityBindingSource;
_entityBindingSource.ListChanged += new ListChangedEventHandler(_entityBindingSource_ListChanged);
_entityDataGridView.RowsRemoved += new DataGridViewRowsRemovedEventHandler(_entityDataGridView_RowsRemoved);
_idFieldName = idFieldName;
_altKeyFieldName = altKeyFieldName;
_dataLoadSql = dataLoadSql; 
}
private DataGridView _entityDataGridView;
private BindingSource _entityBindingSource;
private C _context;
private IQueryable<T> _dataSource;
private bool _loadInProgress;
public void LoadData()
{
try
{
_loadInProgress = true;
_context = (C)Activator.CreateInstance(typeof(C));
_dataSource = _context.Set(typeof(T)).SqlQuery(_dataLoadSql).OfType<T>().AsQueryable<T>(); 
_dataSource.Load();
_entityBindingSource.DataSource = _context.Set(typeof(T)).Local;
_auditTrailItems = new Dictionary<string, AuditTrailItem>();
}
finally
{
_loadInProgress = false;
}
}
public class AuditTrailItem
{
public AuditTrailItem(System.Data.EntityState itemState, T item, string itemKey)
{
this.ItemState = itemState;
this.Item = item;
this.ItemKey = itemKey;
}
public System.Data.EntityState ItemState { get; private set; }
public T Item { get; private set; }
public string ItemKey { get; private set; }
}

// keeps individual data changes audit trail
public Dictionary<string, AuditTrailItem> AuditTrailItems { get { return _auditTrailItems; } }
private Dictionary<string, AuditTrailItem> _auditTrailItems;
private void addAuditTrailItem(T item, System.Data.EntityState state, Dictionary<string, AuditTrailItem> auditTrailItems)
{
string key = getKeyValue(item);
if (string.IsNullOrWhiteSpace(key)) return; 
key = string.Format("{0}:{1}", state, key); 
if (auditTrailItems.ContainsKey(key)) return;
auditTrailItems.Add(key, new AuditTrailItem(state, item, key)); 
}
private void auditTrailModelChanges(ref Dictionary<string, AuditTrailItem> auditTrailItems)
{
if (auditTrailItems == null) auditTrailItems = new Dictionary<string, AuditTrailItem>();
IEnumerable<T>[] checkStateSources = {
(IEnumerable<T>)_context.Set(typeof(T)).Local,
(IEnumerable<T>)_dataSource };
foreach (IEnumerable<T> checkStateSource in checkStateSources)
{
foreach (T item in checkStateSource)
{
switch (_context.Entry(item).State)
{
case System.Data.EntityState.Added:
case System.Data.EntityState.Modified:
case System.Data.EntityState.Deleted:
addAuditTrailItem(item, _context.Entry(item).State, auditTrailItems);
break;
}
}
}
} --- to be continued ---

Среда, 17 апреля 2013, 5:39 +04:00 от Salakhetdinov Shamil <mcp2004 at mail.ru>:
>Hi Scott --
>
>Thank you for your sample. I have prepared mine, which I will post here in several subsequent posts as one posting limit is 20KB.
>
>By "individual changes" I mean *all* the data changes happened between data load and data saving, And I wanted to "capture" that individual data changes as soon as they happen not before .SaveChanges() call.

<<< skipped >>>
>