EF Core set Original Values in Disconnected Scenario - ef-core-2.2

Question

I am using DBContext.Update(ParentEntity) to update an entity. Then I loop through each of the Entities property.CurrentValue and property.OriginalValue.
The problem I am facing is that CurrentValues and OriginalValues are the same even though one Property has been changed and is different from the DB. I was expecting to get OriginalValues from the Database.
Heres the loop that happens before saving changes.
foreach (var entry in ChangeTracker.Entries())
{
if (entry.Entity is Audit || entry.State == EntityState.Detached || entry.State == EntityState.Unchanged ||entry.Entity is ChangelogUser)
continue;
var auditEntry = new AuditEntry(entry) {TableName = entry.Metadata.Relational().TableName};
auditEntries.Add(auditEntry);
foreach (var property in entry.Properties)
{
if (property.IsTemporary)
{
// value will be generated by the database, get the value after saving
auditEntry.TemporaryProperties.Add(property);
continue;
}
string propertyName = property.Metadata.Name;
if (property.Metadata.IsPrimaryKey())
{
auditEntry.KeyValues[propertyName] = property.CurrentValue;
continue;
}
switch (entry.State)
{
case EntityState.Added:
auditEntry.NewValues[propertyName] = property.CurrentValue;
break;
case EntityState.Deleted:
auditEntry.OldValues[propertyName] = property.OriginalValue;
break;
case EntityState.Modified:
if (property.CurrentValue != null)
{
if (property.OriginalValue != null && property.CurrentValue != null)
{
if (property.IsModified && !property.CurrentValue.Equals(property.OriginalValue))
{
auditEntry.OldValues[propertyName] = property.OriginalValue;
auditEntry.NewValues[propertyName] = property.CurrentValue;
}
}
}
break;
}
}
From this code I AWLAYS get the same Original and Current values. Is there some way to get the Original Values from the DB and set them on the Entity?

Answer 1

Since it is suuuper difficult to get an answer for EFCore Questions here´s the solution I came up with.
Check out the State.Modified section. I Iterate through each entity and then iterate through each property. In this case, I am using the current and original values to compare them and only add them to my audit table when something has changed.
At the end of the method I remove the Entities that have not changed from my audit table. Simple mimple.
You could use this the var databaseValues = entry.GetDatabaseValues(); To for your custom disconnected scenario needs.
var auditEntries = new List<AuditEntry>();
foreach (var entry in ChangeTracker.Entries())
{
if (entry.Entity is Audit || entry.State == EntityState.Detached || entry.State == EntityState.Unchanged)
continue;
var auditEntry = new AuditEntry(entry) {TableName = entry.Metadata.Relational().TableName};
auditEntries.Add(auditEntry);
var databaseValues = entry.GetDatabaseValues();
foreach (var property in entry.Properties)
{
if (property.IsTemporary)
{
// value will be generated by the database, get the value after saving
auditEntry.TemporaryProperties.Add(property);
continue;
}
string propertyName = property.Metadata.Name;
if (property.Metadata.IsPrimaryKey())
{
auditEntry.KeyValues[propertyName] = property.CurrentValue;
continue;
}
switch (entry.State)
{
case EntityState.Added:
auditEntry.NewValues[propertyName] = property.CurrentValue;
break;
case EntityState.Deleted:
auditEntry.OldValues[propertyName] = property.OriginalValue;
break;
case EntityState.Modified:
if (property.CurrentValue != null)
{
if (databaseValues[propertyName] != null && property.CurrentValue != null)
{
if (property.IsModified && !property.CurrentValue.Equals(databaseValues[propertyName]))
{
auditEntry.OldValues[propertyName] = databaseValues[propertyName];
auditEntry.NewValues[propertyName] = property.CurrentValue;
}
}
}
break;
}
}
if (auditEntry.NewValues.Equals(auditEntry.OldValues) || auditEntry.NewValues.Count == 0 && auditEntry.OldValues.Count == 0)
{
auditEntries.Remove(auditEntry);
}