Implementing Audit Log / Change History with MVC & Entity Framework

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IF you are using EF 4 you can subscribe to the SavingChanges event.

Since Entities is a partial class you can add additional functionality in a separate file. So create a new file named Entities and there implement the partial method OnContextCreated to hook up the event

public partial class Entities
{
    partial void OnContextCreated()
    {
        SavingChanges += OnSavingChanges;
    }

    void OnSavingChanges(object sender, EventArgs e)
    {

        var modifiedEntities = ObjectStateManager.GetObjectStateEntries(EntityState.Modified);
        foreach (var entry in modifiedEntities)
        {
            var modifiedProps = ObjectStateManager.GetObjectStateEntry(entry.EntityKey).GetModifiedProperties();
            var currentValues = ObjectStateManager.GetObjectStateEntry(entry.EntityKey).CurrentValues;
            foreach (var propName in modifiedProps)
            {
                var newValue = currentValues[propName];
                //log changes
            }
        }
    }
}

If you are using EF 4.1 you can go through this article to extract changes

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