Question
Is there a way to get the original Entity itself from the ChangeTracker (rather than just the original values)?
If the State is Modified, then I suppose I could do this:
// Get the DbEntityEntry from the DbContext.ChangeTracker...
// Store the current values
var currentValues = entry.CurrentValues.Clone();
// Set to the original values
entry.CurrentValues.SetValues(entry.OriginalValues.Clone());
// Now we have the original entity
Foo entity = (Foo)entry.Entity;
// Do something with it...
// Restore the current values
entry.CurrentValues.SetValues(currentValues);
But this doesn't seem very nice, and I'm sure there are problems with it that I don't know about... Is there a better way?
I'm using Entity Framework 6.
Accepted Answer
Override SaveChanges of DbContext or just access ChangeTracker from the context:
foreach (var entry in context.ChangeTracker.Entries<Foo>())
{
if (entry.State == System.Data.EntityState.Modified)
{
// use entry.OriginalValues
Foo originalFoo = CreateWithValues<Foo>(entry.OriginalValues);
}
}
Here is a method which will create a new entity with the original values. Thus all entities should have a parameterless public constructor, you can simply construct an instance with new:
private T CreateWithValues<T>(DbPropertyValues values)
where T : new()
{
T entity = new T();
Type type = typeof(T);
foreach (var name in values.PropertyNames)
{
var property = type.GetProperty(name);
property.SetValue(entity, values.GetValue<object>(name));
}
return entity;
}
Popular Answer
Nice. Here is a slightly modified version that will handle complex properties:
public static TEntity GetOriginal<TEntity>(this DbContext ctx, TEntity updatedEntity) where TEntity : class
{
Func<DbPropertyValues, Type, object> getOriginal = null;
getOriginal = (originalValues, type) =>
{
object original = Activator.CreateInstance(type, true);
foreach (var ptyName in originalValues.PropertyNames)
{
var property = type.GetProperty(ptyName);
object value = originalValues[ptyName];
if (value is DbPropertyValues) //nested complex object
{
property.SetValue(original, getOriginal(value as DbPropertyValues, property.PropertyType));
}
else
{
property.SetValue(original, value);
}
}
return original;
};
return (TEntity)getOriginal(ctx.Entry(updatedEntity).OriginalValues, typeof(TEntity));
}
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