Entity Framework 5 Updating a Record

Question

I have been exploring different methods of editing updating a record within Entity Framework 5 in an ASP NET MVC3 environment  but so far none of them tick all of the boxes I need  I ll explain why   I have found three methods to which I ll mention the pros and cons   Method 1 - Load original record  update each property  var original   db Users Find updatedUser UserId    if  original    null        original BusinessEntityId   updatedUser BusinessEntityId      original Email   updatedUser Email      original EmployeeId   updatedUser EmployeeId      original Forename   updatedUser Forename      original Surname   updatedUser Surname      original Telephone   updatedUser Telephone      original Title   updatedUser Title      original Fax   updatedUser Fax      original ASPNetUserId   updatedUser ASPNetUserId      db SaveChanges            Pros   Can specify which properties change Views don t need to contain every property   Cons   2 x queries on database to load original then update it   Method 2 - Load original record  set changed values  var original   db Users Find updatedUser UserId    if  original    null        db Entry original  CurrentValues SetValues updatedUser       db SaveChanges        Pros   Only modified properties are sent to database   Cons   Views need to contain every property 2 x queries on database to load original then update it   Method 3 - Attach updated record and set state to EntityState Modified  db Users Attach updatedUser   db Entry updatedUser  State   EntityState Modified  db SaveChanges      Pros   1 x query on database to update   Cons   Can t specify which properties change Views must contain every property   Question  My question to you guys  is there a clean way that I can achieve this set of goals    Can specify which properties change Views don t need to contain every property  such as password   1 x query on database to update   I understand this is quite a minor thing to point out but I may be missing a simple solution to this  If not method one will prevail  -

User · Answer

There are some really good answers given already, but I wanted to throw in my two cents. Here is a very simple way to convert a view object into a entity. The simple idea is that only the properties that exist in the view model get written to the entity. This is similar to @Anik Islam Abhi's answer, but has null propagation.

public static T MapVMUpdate<T>(object updatedVM, T original)
{
    PropertyInfo[] originalProps = original.GetType().GetProperties();
    PropertyInfo[] vmProps = updatedVM.GetType().GetProperties();
    foreach (PropertyInfo prop in vmProps)
    {
        PropertyInfo projectProp = originalProps.FirstOrDefault(x => x.Name == prop.Name);
        if (projectProp != null)
        {
            projectProp.SetValue(original, prop.GetValue(updatedVM));
        }
    }
    return original;
}

Pros

Views don't need to have all the properties of the entity.
You never have to update code when you add remove a property to a view.
Completely generic

Cons

2 hits on the database, one to load the original entity, and one to save it.

To me the simplicity and low maintenance requirements of this approach outweigh the added database call.

User · Answer

Depending on your use case  all the above solutions apply  This is how i usually do it however    For server side code  e g  a batch process  I usually load the entities and work with dynamic proxies  Usually in batch processes you need to load the data anyways at the time the service runs  I try to batch load the data instead of using the find method to save some time  Depending on the process I use optimistic or pessimistic concurrency control  I always use optimistic except for parallel execution scenarios where I need to lock some records with plain sql statements  this is rare though   Depending on the code and scenario the impact can be reduced to almost zero   For client side scenarios  you have a few options    Use view models  The models should have a property UpdateStatus unmodified-inserted-updated-deleted   It is the responsibility of the client to set the correct value to this column depending on the user actions  insert-update-delete   The server can either query the db for the original values or the client should send the original values to the server along with the changed rows  The server should attach the original values and use the UpdateStatus column for each row to decide how to handle the new values  In this scenario I always use optimistic concurrency  This will only do the insert - update - delete statements and not any selects  but it might need some clever code to walk the graph and update the entities  depends on your scenario - application   A mapper can help but does not handle the CRUD logic Use a library like breeze js that hides most of this complexity  as described in 1  and try to fit it to your use case     Hope it helps

User · Answer

You are looking for   db Users Attach updatedUser   var entry   db Entry updatedUser   entry Property e   gt  e Email  IsModified   true     other changed properties db SaveChanges

User · Answer

foreach PropertyInfo propertyInfo in original GetType   GetProperties          if  propertyInfo GetValue updatedUser  null     null          propertyInfo SetValue updatedUser  propertyInfo GetValue original  null   null     db Entry original  CurrentValues SetValues updatedUser   db SaveChanges

User · Answer

I really like the accepted answer   I believe there is yet another way to approach this as well   Let s say you have a very short list of properties that you wouldn t want to ever include in a View  so when updating the entity  those would be omitted   Let s say that those two fields are Password and SSN     db Users Attach updatedUser    var entry   db Entry updatedUser   entry State   EntityState Modified   entry Property e   gt  e Password  IsModified   false  entry Property e   gt  e SSN  IsModified   false      db SaveChanges         This example allows you to essentially leave your business logic alone after adding a new field to your Users table and to your View

User · Answer

I have added an extra update method onto my repository base class that s similar to the update method generated by Scaffolding  Instead of setting the entire object to  modified   it sets a set of individual properties   T is a class generic parameter    public void Update T obj  params Expression lt Func lt T  object gt  gt    propertiesToUpdate        Context Set lt T gt    Attach obj        foreach  var p in propertiesToUpdate                Context Entry obj  Property p  IsModified   true            And then to call  for example   public void UpdatePasswordAndEmail long userId  string password  string email        var user   new User  UserId   userId  Password   password  Email   email        Update user  u   gt  u Password  u   gt  u Email        Save        I like one trip to the database  Its probably better to do this with view models  though  in order to avoid repeating sets of properties  I haven t done that yet because I don t know how to avoid bringing the validation messages on my view model validators into my domain project

User · Answer

Just to add to the list of options  You can also grab the object from the database  and use an auto mapping tool like Auto Mapper  to update the parts of the record you want to change

User · Answer

public interface IRepository       void Update lt T gt  T obj  params Expression lt Func lt T  object gt  gt    propertiesToUpdate  where T   class     public class Repository   DbContext  IRepository       public void Update lt T gt  T obj  params Expression lt Func lt T  object gt  gt    propertiesToUpdate  where T   class               Set lt T gt    Attach obj           propertiesToUpdate ToList   ForEach p   gt  Entry obj  Property p  IsModified   true           SaveChanges

[c#] Entity Framework 5 Updating a Record

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