How keep the original model data when execute an Edit on MVC?[Answered] RSS

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  Peter Cong

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  How keep the original model data when execute an Edit on MVC?

  Apr 15, 2019 06:35 PM|Peter Cong|LINK

  I am trying to implement an Audit trail in my mvc web app, the Add and Delete is easy to implement, but I have a problem in Editing an existing record.

  Basically, for each editing, I need to compare each field between current UI field value and the existing value in database, and create a change log in Log table.

  so I am trying to do something like this:

  [HttpPost]
          public ActionResult Edit(ProdViewModel viewModel, string button)
          {
  
              ProdViewModel OrigAIGModel = viewModel; //I want to keep the original model data for comparing later,
              tbl_Production NewProdModel = null;
             .......
  
  
             try
              {
                  if (ModelState.IsValid)
                  {
                    int prodID=  viewModel.SaveChanges();  //Update the record            
  
                      if (prodID > 0)
                      {
                          //after successful update above, I need to compare the data below and create a audit trail.
                        // UpdateAuditTrail(ProdViewModel,NewProdModel.GetByID(prodID));
                      //here I expect to pass the old model data and new model data,
                  //But the ProdViewModel is not the old model data, it is the updated model data, the ProdViewModel and NewProdModel is equivelent, 
                          return RedirectToAction("Edit", new { id = ProdID });
                      }
                  }
               return View(viewModel);
  

  Is there any way to keep the original model data before the  "viewModel.SaveChanges(); ", so I can compare the two models (old model and new model ) data for auditing purpose?

  Or if there is any other better solutions?

  Any help is highly appreciated!

• • Reply
  mgebhard

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  Re: How keep the original model data when execute an Edit on MVC?

  Apr 15, 2019 07:09 PM|mgebhard|LINK

  This should be handled in the database using an UPDATE trigger.

  Google has a lot of information on the subject

  https://stackoverflow.com/questions/12137102/sql-update-trigger-only-when-column-is-modified

  SQL UPDATE Trigger reference

  https://docs.microsoft.com/en-us/sql/t-sql/functions/update-trigger-functions-transact-sql?view=sql-server-2017

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  ryanbesko

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  Re: How keep the original model data when execute an Edit on MVC?

  Apr 15, 2019 07:28 PM|ryanbesko|LINK

  Retrieve the entity from the database first thing in your POST method.

  var fetched = db.Table.Find(id);

  if(fetched.Field != posted.Field)

  {

  ...do something to log

  fetched.Field = posted.Field

  }

  Then just remember to update the fetched entry to the database (instead of the posted one).

  db.entry(fetched).State = EntityState.Modified;

  db.SaveChanges();

  Mark all posts that give the desired result the answer. If you only mark the last that gave you clarification because you misread an earlier post others will be confused. Some of us are here to help others and our point to post ratio matters.
• • Reply
  bruce (sqlwo...

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  Re: How keep the original model data when execute an Edit on MVC?

  Apr 15, 2019 07:33 PM|bruce (sqlwork.com)|LINK

  you should also and an update timestamp, to test if the save was done after the page read, and page post back.

  bruce (sqlwork.com)
• • Reply
  Peter Cong

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  366 Points

  2214 Posts

  Re: How keep the original model data when execute an Edit on MVC?

  Apr 15, 2019 07:35 PM|Peter Cong|LINK

  mgebhard

  This should be handled in the database using an UPDATE trigger.

  Google has a lot of information on the subject

  https://stackoverflow.com/questions/12137102/sql-update-trigger-only-when-column-is-modified

  SQL UPDATE Trigger reference

  https://docs.microsoft.com/en-us/sql/t-sql/functions/update-trigger-functions-transact-sql?view=sql-server-2017

  It seems the Update trigger is doing some coding in SQL side, no quite understand how to apply it in my situation,

  I am wondering if there is any way to do it in controller side based on the C# codes I posted.

  Thanks a lot,

• • Reply
  bruce (sqlwo...

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  Re: How keep the original model data when execute an Edit on MVC?

  Apr 15, 2019 09:43 PM|bruce (sqlwork.com)|LINK

  for an update, your code should lookup the old entity by the encrypted key passed by the post back view model.  then apply the post back view model values that are allowed to be modified by the user to the entity. You can then use change tracking for audit.  then save changes. 

  hint: you can use attributes and reflection to apply changes from the view model to the entity model, or use a tool like automapper.

  bruce (sqlwork.com)
• • Reply
  Peter Cong

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  2214 Posts

  Re: How keep the original model data when execute an Edit on MVC?

  Apr 15, 2019 10:25 PM|Peter Cong|LINK

  bruce (sqlwork.com)

  for an update, your code should lookup the old entity by the encrypted key passed by the post back view model.  then apply the post back view model values that are allowed to be modified by the user to the entity. You can then use change tracking for audit.  then save changes. 

  hint: you can use attributes and reflection to apply changes from the view model to the entity model, or use a tool like automapper.

  Sounds this is a better way, I appreciate if you can provide an example based on my example codes provided, much appreciated,

• • Reply
  Peter Cong

  Member

  366 Points

  2214 Posts

  Re: How keep the original model data when execute an Edit on MVC?

  Apr 16, 2019 06:40 PM|Peter Cong|LINK

  ryanbesko

  Retrieve the entity from the database first thing in your POST method.

  var fetched = db.Table.Find(id);

  if(fetched.Field != posted.Field)

  {

  ...do something to log

  fetched.Field = posted.Field

  }

  Then just remember to update the fetched entry to the database (instead of the posted one).

  db.entry(fetched).State = EntityState.Modified;

  db.SaveChanges();

  Thank you so much, this is an easy and simple solution, works very well.