How to update only modified values (EntityFramework 5.0)? - entity-framework

Question

I have this entity, want to update using entityframework
EmployeeModel employee = new EmployeeModel
{
Id = 1000, //This one must
FirstName = modifiedValue,
Email = modifiedValue,
LastName = originalValue,
Phone = originalValue
};
Code to update
_db.ObjectStateManager.ChangeObjectState(employee, EntityState.Modified);
_db.SaveChanges();
This is the SQL statement got once updated
Update Employee set Id=1138,FirstName='modifiedValue',Email='modifiedValue',LastName= 'OriginalValue',phone='originalValue' where Id=1138
But I am expecting this
Update Employee set FirstName='modifiedValue', Email='modifiedValue' where Id=1138.
I dont know what I am missing here. Please let me know.

Answer 1

This problem is common when dealing with DTOs. An employee entity is fetched from the database, mapped to a DTO and sent over the wire. The client then modifies this DTO and sends it back to the server.
When you touch (set) a property on an EF entity, EF will assume that the value has been changed. Even if the old value and the new value are exactly the same.
The same problem occurs when you map the DTO to a new Entity and attach it to EF and updating its status to 'Modified'.
Using AutoMapper:
// This will result in the full update statement
var employee = AutoMapper.Mapper.Map<EmployeeDto, Employee>(dto);
// This will result in a smaller update statement (only actual changes)
var employee = dbContext.Employees.Find(dto.Id);
AutoMapper.Mapper.Map(dto, employee);
Or, manually (I would avoid doing this, but just for the sake of completeness):
// This will result in a smaller update statement (only actual changes)
var employee = dbContext.Employees.Find(dto.Id);
if (employee.Email != dto.Email )
employee.Email = dto.Email;
There are probably some other ways for dealing with this problem... but using AutoMapper together with Entity Framework correctly is definitely one of the easiest ways.

Answer 2

This is the solution I got
var entity = _db.CreateObjectSet<Employee>();
entity.Detach(employee);
entity.Attach(employee);
foreach (string modifiedPro in employeeModel.ModifiedProperties){
_db.ObjectStateManager.GetObjectStateEntry(employee).SetModifiedProperty(modifiedPro);}
_db.SaveChanges();
Only modified values in the sql update statement
Update Employee set FirstName='modifiedValue', Email='modifiedValue' where Id=1138.
If anybody knows better answer than this, Please post your suggestions

Answer 3

You can try this way
public update(Person model)
{
// Here model is model return from form on post
var oldobj = db.Person.where(x=>x.ID = model.ID).SingleOrDefault();
var UpdatedObj = (Person) Entity.CheckUpdateObject(oldobj, model);
db.Entry(oldobj).CurrentValues.SetValues(UpdatedObj);
}
public static object CheckUpdateObject(object originalObj, object updateObj)
{
foreach (var property in updateObj.GetType().GetProperties())
{
if (property.GetValue(updateObj, null) == null)
{
property.SetValue(updateObj,originalObj.GetType().GetProperty(property.Name)
.GetValue(originalObj, null));
}
}
return updateObj;
}