Hold Old and New value in SaveChange as DbEntityEntry.Entity to Audit

问题

As you know we can Audit object in SaveChange() but I have some problem with Modified and Deleted entities as following,

First I am using Audit.Net(this is very simple to use) to Audit my objects the below method should do audit as:

 private int SaveAuditRecord(DbEntityEntry dbEntry, string userGUID)
    {
        Logging.Log(LoggingMode.Error, "Saving Audid Entry{0}....", dbEntry.ToString());
        DateTime changeTime = DateTime.UtcNow;
        TableAttribute tableAttr = dbEntry.Entity.GetType().GetCustomAttributes(typeof(TableAttribute), true).SingleOrDefault() as TableAttribute;
        string tableName = tableAttr != null ? tableAttr.Name : dbEntry.Entity.GetType().Name;
        Logging.Log(LoggingMode.Error, "TableName Retrived {0}...", tableName);
        switch (dbEntry.State)
        {
            case System.Data.Entity.EntityState.Added:
                int result = base.SaveChanges(); 
                AuditNet.AuditMonoAction("Add " + tableName, userGUID, dbEntry.Entity);
                return result;
            case System.Data.Entity.EntityState.Deleted:
                AuditNet.AuditMonoAction("Delete " + tableName, userGUID, dbEntry.Entity);
                break;
            case System.Data.Entity.EntityState.Modified:
                int modifiedResult = 0;
                var primaryKey = GetPrimaryKeyValue(dbEntry);
                modifiedResult = base.SaveChanges(); 
                object entity2Audit = dbEntry.Entity;//Hold the current entity here and change it in below Audit using block
                using (var audit = Audit.Core.AuditScope.Create("Edit " + tableName, () => dbEntry.Entity))
                { 
                    audit.SetCustomField("UserGUID", userGUID, false);  
                    foreach (var prop in dbEntry.OriginalValues.PropertyNames)
                    {
                        var originalValue = dbEntry.OriginalValues[prop].ToString();
                        var currentValue = dbEntry.CurrentValues[prop].ToString();
                        if (originalValue != currentValue)
                            Logging.Log(LoggingMode.Error, "Prop {0} get originalValue :{1} , currentValue:{2}", prop, originalValue, currentValue);
                    } 
                }
                return modifiedResult;
            default:
                break;
        }
        return base.SaveChanges();
    }

1- For Added state there is no problem with because I am auditing dbEntry.Entity which I think contains Current Values always.

2- For Delete and Modify there is some problems,

Delete: I think as I am auditing dbEntry.Entity, it is looking for current value and raise the exception:

CurrentValues cannot be used for entities in the Deleted state.

Modify: always OldValue and NewValue always are the same as CurrentValue as I mentioned above.

So my main question is How can I do it for Delete and Modify like dbEntry.Entity?

P.S: in Using block we can change audit object to set NewValue as Audit.Net mentioned.

UPDATE1:

Even with this code Old and New value always are the same :

 int modRes = 0;
                object entity2Audit = dbEntry.Entity;//Hold the current entity here and change it in below Audit using block
                DbEntityEntry dbEntryTemp = dbEntry;
                foreach (var prop in dbEntryTemp.OriginalValues.PropertyNames)
                {
                    var originalValue = dbEntry.OriginalValues[prop].ToString();
                    var currentValue = dbEntry.CurrentValues[prop].ToString();
                    if (originalValue != currentValue)
                    {
                        Logging.Log(LoggingMode.Error, "Prop11 {0} get originalValue :{1} , currentValue:{2}", prop, originalValue, currentValue);
                        dbEntryTemp.CurrentValues[prop] = dbEntryTemp.OriginalValues[prop] = originalValue;
                    }
                } 
                object en = dbEntryTemp.Entity;
                using (var audit = Audit.Core.AuditScope.Create("Edit " + tableName, () => en))
                {
                    modRes = base.SaveChanges();
                    audit.SetCustomField("UserGUID", userGUID, false);
                    audit.SetCustomField("NewValue", dbEntry.Entity, false);
                    audit.SetCustomField("OldValue", en, false);
                    en = dbEntry.Entity;
                }

回答1:

First I should thanks to thepirat000 who made Audit.Net lib, this is very nice lib to Audit with many option as he mentioned in GitHub

but about my problem, this is my first time to override SaveChange() and I didn't know DbEntityEntry object as well, but the solution seems so funny, just need to convert CurrentValues and OriginalValues to Object(), in modify case I am getting the old value by dbEntry.OriginalValues.ToObject() and change it with dbEntry.CurrentValues.ToObject() in Audit.Net scope, that is all.

  Logging.Log(LoggingMode.Prompt, "Saving Audid Entry{0}....", dbEntry.ToString()); 
        TableAttribute tableAttr = dbEntry.Entity.GetType().GetCustomAttributes(typeof(TableAttribute), true).SingleOrDefault() as TableAttribute;
        string tableName = tableAttr != null ? tableAttr.Name : dbEntry.Entity.GetType().Name;
        Logging.Log(LoggingMode.Prompt, "TableName Retrived {0}...", tableName);
        switch (dbEntry.State)
        {
            case System.Data.Entity.EntityState.Added:
                int result = base.SaveChanges();
                object addedObj = dbEntry.Entity;
                using (var audit = Audit.Core.AuditScope.Create("Add " + tableName, () =>addedObj ))
                {
                    audit.SetCustomField("UserGUID", userGUID);
                    addedObj = null;
                } 
                return result;
            case System.Data.Entity.EntityState.Deleted:
                object deletedObj = dbEntry.Entity;
                using (var audit = Audit.Core.AuditScope.Create("Delete " + tableName, () => deletedObj))
                {
                    audit.SetCustomField("UserGUID", userGUID);
                    deletedObj = null;
                }  
                break;
            case System.Data.Entity.EntityState.Modified: 
                object en = dbEntry.OriginalValues.ToObject();
                using (var audit = Audit.Core.AuditScope.Create("Edit " + tableName, () => en))
                {
                    audit.SetCustomField("UserGUID", userGUID);
                    en = dbEntry.CurrentValues.ToObject();
                }
                break;
            default:
                break;
        }
        return base.SaveChanges();

来源：https://stackoverflow.com/questions/43466550/hold-old-and-new-value-in-savechange-as-dbentityentry-entity-to-audit