Get default audit field behavior with an external datasource

Question

Others have posted and blogged extensively about creating a robust audit trail for LightSwitch. However, if you are looking to achieve the default behavior with an external datasource, you could simply add the fields to your database
and write code in every entity's Inserting() and Updating() method.  However, if you have many tables in your app this can be a lot of work.  Here is a very easy way to DRY this up. 
1. Add the audit fields to your tables
- CreatedBy
- DateCreated
- UpdatedBy
- DateUpdated
2. Use this code in the DataService class for your datasource.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.LightSwitch;
using Microsoft.LightSwitch.Security.Server;
namespace LightSwitchApplication
public partial class ApplicationDataService
partial void SaveChanges_Executing()
EntityChangeSet changes = this.Details.GetChanges();
IReadOnlyCollection<IEntityObject> addedEntities = changes.AddedEntities;
IReadOnlyCollection<IEntityObject> modifiedEntities = changes.ModifiedEntities;
if (addedEntities.Any())
foreach (IEntityObject entity in addedEntities)
InsertAuditFields(entity);
if (modifiedEntities.Any())
foreach (IEntityObject entity in modifiedEntities)
UpdateAuditFields(entity);
private void InsertAuditFields(IEntityObject entity)
string userName = this.Application.User.FullName;
DateTimeOffset currentDateTime = DateTimeOffset.Now;
entity.Details.Properties["CreatedBy"].Value = userName;
entity.Details.Properties["DateCreated"].Value = currentDateTime;
entity.Details.Properties["UpdatedBy"].Value = userName;
entity.Details.Properties["DateUpdated"].Value = currentDateTime;
private void UpdateAuditFields(IEntityObject entity)
string userName = this.Application.User.FullName;
DateTimeOffset currentDateTime = DateTimeOffset.Now;
entity.Details.Properties["UpdatedBy"].Value = userName;
entity.Details.Properties["DateUpdated"].Value = currentDateTime;
Hopefully this helps someone.

Answer 1

This version will check whether the table has the audit properties, thus allowing you to opt in.  Paul's solution is going to be better in the long run because it checks at compile time.  This was meant to be a quick way to get the default behavior. 
This is not a substitute for a full audit capability (see Paul's blog) if that is your requirement.
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.LightSwitch;
using Microsoft.LightSwitch.Security.Server;
using Microsoft.LightSwitch.Details;
namespace LightSwitchApplication
public partial class ApplicationDataService
partial void SaveChanges_Executing()
EntityChangeSet changes = this.Details.GetChanges();
IReadOnlyCollection<IEntityObject> addedEntities = changes.AddedEntities;
IReadOnlyCollection<IEntityObject> modifiedEntities = changes.ModifiedEntities;
if (addedEntities.Any())
foreach (IEntityObject entity in addedEntities)
if (AuditProperties(entity))
InsertAuditFields(entity);
if (modifiedEntities.Any())
foreach (IEntityObject entity in modifiedEntities)
if (AuditProperties(entity))
UpdateAuditFields(entity);
private bool AuditProperties(IEntityObject entity)
bool hasAuditProperties = true;
bool createdBy = entity.Details.Properties.Contains("CreatedBy");
bool dateCreated = entity.Details.Properties.Contains("DateCreated");
bool updatedBy = entity.Details.Properties.Contains("UpdatedBy");
bool dateUpdated = entity.Details.Properties.Contains("DateUpdated");
bool[] checkForAuditProperties = new bool[]
createdBy,
dateCreated,
updatedBy,
dateUpdated
if (checkForAuditProperties.Any(a => a == false))
hasAuditProperties = false;
return hasAuditProperties;
private void InsertAuditFields(IEntityObject entity)
string userName = this.Application.User.FullName;
DateTimeOffset currentDateTime = DateTimeOffset.Now;
entity.Details.Properties["CreatedBy"].Value = userName;
entity.Details.Properties["DateCreated"].Value = currentDateTime;
entity.Details.Properties["UpdatedBy"].Value = userName;
entity.Details.Properties["DateUpdated"].Value = currentDateTime;
private void UpdateAuditFields(IEntityObject entity)
string userName = this.Application.User.FullName;
DateTimeOffset currentDateTime = DateTimeOffset.Now;
entity.Details.Properties["UpdatedBy"].Value = userName;
entity.Details.Properties["DateUpdated"].Value = currentDateTime;